Merge lp:~corey.bryant/ubuntu/vivid/python-pint/0.6 into lp:ubuntu/vivid/python-pint

[Corey Bryant]

[Martin Pitt (pitti)]

This already got uploaded without closing this MP: https://launchpad.net/ubuntu/+source/python-pint/0.6-0ubuntu1

=== removed file '.gitignore'
--- .gitignore	2014-09-05 23:26:05 +0000
+++ .gitignore	1970-01-01 00:00:00 +0000
@@ -1,14 +0,0 @@
-*~
-__pycache__
-*egg-info*
-*.pyc
-.DS_Store
-docs/_build/
-.idea
-build/
-dist/
-MANIFEST
-.tox
-
-# WebDAV file system cache files
-.DAV/
 
=== removed file '.pc/applied-patches'
--- .pc/applied-patches	2014-09-05 23:26:05 +0000
+++ .pc/applied-patches	1970-01-01 00:00:00 +0000
@@ -1,2 +0,0 @@
-no-intersphinx.patch
-removes-privacy-breach-in-doc.patch
 
=== removed directory '.pc/no-intersphinx.patch'
=== removed directory '.pc/no-intersphinx.patch/docs'
=== removed file '.pc/no-intersphinx.patch/docs/conf.py'
--- .pc/no-intersphinx.patch/docs/conf.py	2014-09-05 23:26:05 +0000
+++ .pc/no-intersphinx.patch/docs/conf.py	1970-01-01 00:00:00 +0000
@@ -1,299 +0,0 @@
-#!/usr/bin/env python3
-# -*- coding: utf-8 -*-
-#
-# pint documentation build configuration file, created by
-# sphinx-quickstart on Thu Mar  1 13:33:14 2012.
-#
-# This file is execfile()d with the current directory set to its containing dir.
-#
-# Note that not all possible configuration values are present in this
-# autogenerated file.
-#
-# All configuration values have a default; values that are commented out
-# serve to show the default.
-
-import sys, os
-import pkg_resources
-import datetime
-
-# If extensions (or modules to document with autodoc) are in another directory,
-# add these directories to sys.path here. If the directory is relative to the
-# documentation root, use os.path.abspath to make it absolute, like shown here.
-#sys.path.insert(0, os.path.abspath('.'))
-
-# -- General configuration -----------------------------------------------------
-
-# If your documentation needs a minimal Sphinx version, state it here.
-#needs_sphinx = '1.0'
-
-# Add any Sphinx extension module names here, as strings. They can be extensions
-# coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.autodoc', 'sphinx.ext.doctest', 'sphinx.ext.intersphinx', 'sphinx.ext.coverage', 'sphinx.ext.viewcode', 'sphinx.ext.mathjax']
-
-# Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
-
-# The suffix of source filenames.
-source_suffix = '.rst'
-
-# The encoding of source files.
-#source_encoding = 'utf-8-sig'
-
-# The master toctree document.
-master_doc = 'index'
-
-# General information about the project.
-project = 'pint'
-author = 'Hernan E. Grecco'
-
-# The version info for the project you're documenting, acts as replacement for
-# |version| and |release|, also used in various other places throughout the
-# built documents.
-
-version = pkg_resources.get_distribution(project).version
-release = version
-this_year = datetime.date.today().year
-copyright = '%s, %s' % (this_year, author)
-
-# The language for content autogenerated by Sphinx. Refer to documentation
-# for a list of supported languages.
-#language = None
-
-# There are two options for replacing |today|: either, you set today to some
-# non-false value, then it is used:
-#today = ''
-# Else, today_fmt is used as the format for a strftime call.
-#today_fmt = '%B %d, %Y'
-
-# List of patterns, relative to source directory, that match files and
-# directories to ignore when looking for source files.
-exclude_patterns = ['_build']
-
-# The reST default role (used for this markup: `text`) to use for all documents.
-#default_role = None
-
-# If true, '()' will be appended to :func: etc. cross-reference text.
-#add_function_parentheses = True
-
-# If true, the current module name will be prepended to all description
-# unit titles (such as .. function::).
-#add_module_names = True
-
-# If true, sectionauthor and moduleauthor directives will be shown in the
-# output. They are ignored by default.
-#show_authors = False
-
-# The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
-
-# A list of ignored prefixes for module index sorting.
-#modindex_common_prefix = []
-
-
-# -- Options for HTML output ---------------------------------------------------
-
-# The theme to use for HTML and HTML Help pages.  See the documentation for
-# a list of builtin themes.
-#html_theme = 'default'
-html_theme = 'flask'
-
-# Theme options are theme-specific and customize the look and feel of a theme
-# further.  For a list of options available for each theme, see the
-# documentation.
-#html_theme_options = {}
-
-# Add any paths that contain custom themes here, relative to this directory.
-#html_theme_path = []
-html_theme_path = ['_themes']
-
-# The name for this set of Sphinx documents.  If None, it defaults to
-# "<project> v<release> documentation".
-#html_title = None
-
-# A shorter title for the navigation bar.  Default is the same as html_title.
-#html_short_title = None
-
-# The name of an image file (relative to this directory) to place at the top
-# of the sidebar.
-#html_logo = None
-
-# The name of an image file (within the static path) to use as favicon of the
-# docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
-# pixels large.
-#html_favicon = None
-
-# Add any paths that contain custom static files (such as style sheets) here,
-# relative to this directory. They are copied after the builtin static files,
-# so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
-
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-#html_last_updated_fmt = '%b %d, %Y'
-
-# If true, SmartyPants will be used to convert quotes and dashes to
-# typographically correct entities.
-#html_use_smartypants = True
-
-# Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
-html_sidebars = {
-    'index':    ['sidebarintro.html', 'sourcelink.html', 'searchbox.html'],
-    '**':       ['sidebarlogo.html', 'localtoc.html', 'relations.html',
-                 'sourcelink.html', 'searchbox.html']
-}
-
-# Additional templates that should be rendered to pages, maps page names to
-# template names.
-#html_additional_pages = {}
-
-# If false, no module index is generated.
-#html_domain_indices = True
-
-# If false, no index is generated.
-#html_use_index = True
-
-# If true, the index is split into individual pages for each letter.
-#html_split_index = False
-
-# If true, links to the reST sources are added to the pages.
-#html_show_sourcelink = True
-
-# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
-#html_show_sphinx = True
-
-# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
-#html_show_copyright = True
-
-# If true, an OpenSearch description file will be output, and all pages will
-# contain a <link> tag referring to it.  The value of this option must be the
-# base URL from which the finished HTML is served.
-#html_use_opensearch = ''
-
-# This is the file name suffix for HTML files (e.g. ".xhtml").
-#html_file_suffix = None
-
-# Output file base name for HTML help builder.
-htmlhelp_basename = 'pintdoc'
-
-
-# -- Options for LaTeX output --------------------------------------------------
-
-latex_elements = {
-# The paper size ('letterpaper' or 'a4paper').
-#'papersize': 'letterpaper',
-
-# The font size ('10pt', '11pt' or '12pt').
-#'pointsize': '10pt',
-
-# Additional stuff for the LaTeX preamble.
-#'preamble': '',
-}
-
-# Grouping the document tree into LaTeX files. List of tuples
-# (source start file, target name, title, author, documentclass [howto/manual]).
-latex_documents = [
-  ('index', 'pint.tex', 'pint Documentation',
-   'Hernan E. Grecco', 'manual'),
-]
-
-# The name of an image file (relative to this directory) to place at the top of
-# the title page.
-#latex_logo = None
-
-# For "manual" documents, if this is true, then toplevel headings are parts,
-# not chapters.
-#latex_use_parts = False
-
-# If true, show page references after internal links.
-#latex_show_pagerefs = False
-
-# If true, show URL addresses after external links.
-#latex_show_urls = False
-
-# Documents to append as an appendix to all manuals.
-#latex_appendices = []
-
-# If false, no module index is generated.
-#latex_domain_indices = True
-
-
-# -- Options for manual page output --------------------------------------------
-
-# One entry per manual page. List of tuples
-# (source start file, name, description, authors, manual section).
-man_pages = [
-    ('index', 'pint', 'pint Documentation',
-     ['Hernan E. Grecco'], 1)
-]
-
-# If true, show URL addresses after external links.
-#man_show_urls = False
-
-
-# -- Options for Texinfo output ------------------------------------------------
-
-# Grouping the document tree into Texinfo files. List of tuples
-# (source start file, target name, title, author,
-#  dir menu entry, description, category)
-texinfo_documents = [
-  ('index', 'pint', 'pint Documentation',
-   'Hernan E. Grecco', 'pint', 'One line description of project.',
-   'Miscellaneous'),
-]
-
-# Documents to append as an appendix to all manuals.
-#texinfo_appendices = []
-
-# If false, no module index is generated.
-#texinfo_domain_indices = True
-
-# How to display URL addresses: 'footnote', 'no', or 'inline'.
-#texinfo_show_urls = 'footnote'
-
-
-# -- Options for Epub output ---------------------------------------------------
-
-# Bibliographic Dublin Core info.
-epub_title = project
-epub_author = author
-epub_publisher = author
-epub_copyright = copyright
-
-# The language of the text. It defaults to the language option
-# or en if the language is not set.
-#epub_language = ''
-
-# The scheme of the identifier. Typical schemes are ISBN or URL.
-#epub_scheme = ''
-
-# The unique identifier of the text. This can be a ISBN number
-# or the project homepage.
-#epub_identifier = ''
-
-# A unique identification for the text.
-#epub_uid = ''
-
-# A tuple containing the cover image and cover page html template filenames.
-#epub_cover = ()
-
-# HTML files that should be inserted before the pages created by sphinx.
-# The format is a list of tuples containing the path and title.
-#epub_pre_files = []
-
-# HTML files shat should be inserted after the pages created by sphinx.
-# The format is a list of tuples containing the path and title.
-#epub_post_files = []
-
-# A list of files that should not be packed into the epub file.
-#epub_exclude_files = []
-
-# The depth of the table of contents in toc.ncx.
-#epub_tocdepth = 3
-
-# Allow duplicate toc entries.
-#epub_tocdup = True
-
-
-# Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'http://docs.python.org/': None}
 
=== removed directory '.pc/removes-privacy-breach-in-doc.patch'
=== removed directory '.pc/removes-privacy-breach-in-doc.patch/docs'
=== removed directory '.pc/removes-privacy-breach-in-doc.patch/docs/_themes'
=== removed directory '.pc/removes-privacy-breach-in-doc.patch/docs/_themes/flask'
=== removed file '.pc/removes-privacy-breach-in-doc.patch/docs/_themes/flask/layout.html'
--- .pc/removes-privacy-breach-in-doc.patch/docs/_themes/flask/layout.html	2014-09-05 23:26:05 +0000
+++ .pc/removes-privacy-breach-in-doc.patch/docs/_themes/flask/layout.html	1970-01-01 00:00:00 +0000
@@ -1,30 +0,0 @@
-{%- extends "basic/layout.html" %}
-{%- block extrahead %}
-  {{ super() }}
-  {% if theme_touch_icon %}
-  <link rel="apple-touch-icon" href="{{ pathto('_static/' ~ theme_touch_icon, 1) }}" />
-  {% endif %}
-  <link media="only screen and (max-device-width: 480px)" href="{{
-    pathto('_static/small_flask.css', 1) }}" type= "text/css" rel="stylesheet" />
-{% endblock %}
-{%- block relbar2 %}
-  {% if theme_github_fork %}
-    <a href="http://github.com/{{ theme_github_fork }}"><img style="position: fixed; top: 0; right: 0; border: 0;"
-    src="http://s3.amazonaws.com/github/ribbons/forkme_right_darkblue_121621.png" alt="Fork me on GitHub" /></a>
-  {% endif %}
-{% endblock %}
-{% block header %}
-  {{ super() }}
-  {% if pagename == 'index' %}
-  <div>
-  {% endif %}
-{% endblock %}
-{%- block footer %}
-  <div class="footer">
-    &copy; Copyright {{ copyright }}. Pint {{ version }}.
-    Created using <a href="http://sphinx.pocoo.org/">Sphinx</a>.
-  </div>
-  {% if pagename == 'index' %}
-  </div>
-  {% endif %}
-{%- endblock %}
 
=== removed file '.pc/removes-privacy-breach-in-doc.patch/docs/conf.py'
--- .pc/removes-privacy-breach-in-doc.patch/docs/conf.py	2014-09-05 23:26:05 +0000
+++ .pc/removes-privacy-breach-in-doc.patch/docs/conf.py	1970-01-01 00:00:00 +0000
@@ -1,299 +0,0 @@
-#!/usr/bin/env python3
-# -*- coding: utf-8 -*-
-#
-# pint documentation build configuration file, created by
-# sphinx-quickstart on Thu Mar  1 13:33:14 2012.
-#
-# This file is execfile()d with the current directory set to its containing dir.
-#
-# Note that not all possible configuration values are present in this
-# autogenerated file.
-#
-# All configuration values have a default; values that are commented out
-# serve to show the default.
-
-import sys, os
-import pkg_resources
-import datetime
-
-# If extensions (or modules to document with autodoc) are in another directory,
-# add these directories to sys.path here. If the directory is relative to the
-# documentation root, use os.path.abspath to make it absolute, like shown here.
-#sys.path.insert(0, os.path.abspath('.'))
-
-# -- General configuration -----------------------------------------------------
-
-# If your documentation needs a minimal Sphinx version, state it here.
-#needs_sphinx = '1.0'
-
-# Add any Sphinx extension module names here, as strings. They can be extensions
-# coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.autodoc', 'sphinx.ext.doctest', 'sphinx.ext.coverage', 'sphinx.ext.viewcode', 'sphinx.ext.mathjax']
-
-# Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
-
-# The suffix of source filenames.
-source_suffix = '.rst'
-
-# The encoding of source files.
-#source_encoding = 'utf-8-sig'
-
-# The master toctree document.
-master_doc = 'index'
-
-# General information about the project.
-project = 'pint'
-author = 'Hernan E. Grecco'
-
-# The version info for the project you're documenting, acts as replacement for
-# |version| and |release|, also used in various other places throughout the
-# built documents.
-
-version = pkg_resources.get_distribution(project).version
-release = version
-this_year = datetime.date.today().year
-copyright = '%s, %s' % (this_year, author)
-
-# The language for content autogenerated by Sphinx. Refer to documentation
-# for a list of supported languages.
-#language = None
-
-# There are two options for replacing |today|: either, you set today to some
-# non-false value, then it is used:
-#today = ''
-# Else, today_fmt is used as the format for a strftime call.
-#today_fmt = '%B %d, %Y'
-
-# List of patterns, relative to source directory, that match files and
-# directories to ignore when looking for source files.
-exclude_patterns = ['_build']
-
-# The reST default role (used for this markup: `text`) to use for all documents.
-#default_role = None
-
-# If true, '()' will be appended to :func: etc. cross-reference text.
-#add_function_parentheses = True
-
-# If true, the current module name will be prepended to all description
-# unit titles (such as .. function::).
-#add_module_names = True
-
-# If true, sectionauthor and moduleauthor directives will be shown in the
-# output. They are ignored by default.
-#show_authors = False
-
-# The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
-
-# A list of ignored prefixes for module index sorting.
-#modindex_common_prefix = []
-
-
-# -- Options for HTML output ---------------------------------------------------
-
-# The theme to use for HTML and HTML Help pages.  See the documentation for
-# a list of builtin themes.
-#html_theme = 'default'
-html_theme = 'flask'
-
-# Theme options are theme-specific and customize the look and feel of a theme
-# further.  For a list of options available for each theme, see the
-# documentation.
-#html_theme_options = {}
-
-# Add any paths that contain custom themes here, relative to this directory.
-#html_theme_path = []
-html_theme_path = ['_themes']
-
-# The name for this set of Sphinx documents.  If None, it defaults to
-# "<project> v<release> documentation".
-#html_title = None
-
-# A shorter title for the navigation bar.  Default is the same as html_title.
-#html_short_title = None
-
-# The name of an image file (relative to this directory) to place at the top
-# of the sidebar.
-#html_logo = None
-
-# The name of an image file (within the static path) to use as favicon of the
-# docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
-# pixels large.
-#html_favicon = None
-
-# Add any paths that contain custom static files (such as style sheets) here,
-# relative to this directory. They are copied after the builtin static files,
-# so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
-
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-#html_last_updated_fmt = '%b %d, %Y'
-
-# If true, SmartyPants will be used to convert quotes and dashes to
-# typographically correct entities.
-#html_use_smartypants = True
-
-# Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
-html_sidebars = {
-    'index':    ['sidebarintro.html', 'sourcelink.html', 'searchbox.html'],
-    '**':       ['sidebarlogo.html', 'localtoc.html', 'relations.html',
-                 'sourcelink.html', 'searchbox.html']
-}
-
-# Additional templates that should be rendered to pages, maps page names to
-# template names.
-#html_additional_pages = {}
-
-# If false, no module index is generated.
-#html_domain_indices = True
-
-# If false, no index is generated.
-#html_use_index = True
-
-# If true, the index is split into individual pages for each letter.
-#html_split_index = False
-
-# If true, links to the reST sources are added to the pages.
-#html_show_sourcelink = True
-
-# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
-#html_show_sphinx = True
-
-# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
-#html_show_copyright = True
-
-# If true, an OpenSearch description file will be output, and all pages will
-# contain a <link> tag referring to it.  The value of this option must be the
-# base URL from which the finished HTML is served.
-#html_use_opensearch = ''
-
-# This is the file name suffix for HTML files (e.g. ".xhtml").
-#html_file_suffix = None
-
-# Output file base name for HTML help builder.
-htmlhelp_basename = 'pintdoc'
-
-
-# -- Options for LaTeX output --------------------------------------------------
-
-latex_elements = {
-# The paper size ('letterpaper' or 'a4paper').
-#'papersize': 'letterpaper',
-
-# The font size ('10pt', '11pt' or '12pt').
-#'pointsize': '10pt',
-
-# Additional stuff for the LaTeX preamble.
-#'preamble': '',
-}
-
-# Grouping the document tree into LaTeX files. List of tuples
-# (source start file, target name, title, author, documentclass [howto/manual]).
-latex_documents = [
-  ('index', 'pint.tex', 'pint Documentation',
-   'Hernan E. Grecco', 'manual'),
-]
-
-# The name of an image file (relative to this directory) to place at the top of
-# the title page.
-#latex_logo = None
-
-# For "manual" documents, if this is true, then toplevel headings are parts,
-# not chapters.
-#latex_use_parts = False
-
-# If true, show page references after internal links.
-#latex_show_pagerefs = False
-
-# If true, show URL addresses after external links.
-#latex_show_urls = False
-
-# Documents to append as an appendix to all manuals.
-#latex_appendices = []
-
-# If false, no module index is generated.
-#latex_domain_indices = True
-
-
-# -- Options for manual page output --------------------------------------------
-
-# One entry per manual page. List of tuples
-# (source start file, name, description, authors, manual section).
-man_pages = [
-    ('index', 'pint', 'pint Documentation',
-     ['Hernan E. Grecco'], 1)
-]
-
-# If true, show URL addresses after external links.
-#man_show_urls = False
-
-
-# -- Options for Texinfo output ------------------------------------------------
-
-# Grouping the document tree into Texinfo files. List of tuples
-# (source start file, target name, title, author,
-#  dir menu entry, description, category)
-texinfo_documents = [
-  ('index', 'pint', 'pint Documentation',
-   'Hernan E. Grecco', 'pint', 'One line description of project.',
-   'Miscellaneous'),
-]
-
-# Documents to append as an appendix to all manuals.
-#texinfo_appendices = []
-
-# If false, no module index is generated.
-#texinfo_domain_indices = True
-
-# How to display URL addresses: 'footnote', 'no', or 'inline'.
-#texinfo_show_urls = 'footnote'
-
-
-# -- Options for Epub output ---------------------------------------------------
-
-# Bibliographic Dublin Core info.
-epub_title = project
-epub_author = author
-epub_publisher = author
-epub_copyright = copyright
-
-# The language of the text. It defaults to the language option
-# or en if the language is not set.
-#epub_language = ''
-
-# The scheme of the identifier. Typical schemes are ISBN or URL.
-#epub_scheme = ''
-
-# The unique identifier of the text. This can be a ISBN number
-# or the project homepage.
-#epub_identifier = ''
-
-# A unique identification for the text.
-#epub_uid = ''
-
-# A tuple containing the cover image and cover page html template filenames.
-#epub_cover = ()
-
-# HTML files that should be inserted before the pages created by sphinx.
-# The format is a list of tuples containing the path and title.
-#epub_pre_files = []
-
-# HTML files shat should be inserted after the pages created by sphinx.
-# The format is a list of tuples containing the path and title.
-#epub_post_files = []
-
-# A list of files that should not be packed into the epub file.
-#epub_exclude_files = []
-
-# The depth of the table of contents in toc.ncx.
-#epub_tocdepth = 3
-
-# Allow duplicate toc entries.
-#epub_tocdup = True
-
-
-# Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'http://docs.python.org/': None}
 
=== removed file '.travis.yml'
--- .travis.yml	2014-09-05 23:26:05 +0000
+++ .travis.yml	1970-01-01 00:00:00 +0000
@@ -1,65 +0,0 @@
-language: python
-
-python:
-  - "2.6"
-  - "2.7"
-  - "3.2"
-  - "3.3"
-  - "3.4"
-
-env:
-  - UNCERTAINTIES="N" NUMPY_VERSION=0
-  - UNCERTAINTIES="N" NUMPY_VERSION=1.6.2
-  - UNCERTAINTIES="N" NUMPY_VERSION=1.7.1
-  - UNCERTAINTIES="N" NUMPY_VERSION=1.8.1
-  - UNCERTAINTIES="Y" NUMPY_VERSION=0
-  - UNCERTAINTIES="Y" NUMPY_VERSION=1.6.2
-  - UNCERTAINTIES="Y" NUMPY_VERSION=1.7.1
-  - UNCERTAINTIES="Y" NUMPY_VERSION=1.8.1
-
-branches:
-  only:
-    - master
-    - develop
-
-before_install:
-  - wget http://repo.continuum.io/miniconda/Miniconda-latest-Linux-x86_64.sh -O miniconda.sh
-  - chmod +x miniconda.sh
-  - ./miniconda.sh -b
-  - export PATH=/home/travis/miniconda/bin:$PATH
-  - conda update --yes conda
-
-  # The next couple lines fix a crash with multiprocessing on Travis and are not specific to using Miniconda
-  - sudo rm -rf /dev/shm
-  - sudo ln -s /run/shm /dev/shm
-
-install:
-  - conda create -c mwcraig --yes -n env_name python=$TRAVIS_PYTHON_VERSION pip
-  - source activate env_name
-  - if [ $TRAVIS_PYTHON_VERSION == '2.6' ]; then pip install unittest2; fi
-  - if [ $UNCERTAINTIES == 'Y' ]; then pip install uncertainties; fi
-  - if [ $NUMPY_VERSION != '0' ]; then conda install -c mwcraig --yes numpy==$NUMPY_VERSION; fi
-  - pip install coverage coveralls
-
-script:
-  - coverage run -p --source=pint --omit="*test*","*compat*" setup.py test
-  - coverage combine
-  - coverage report -m
-
-after_script:
-  - coveralls --verbose
-
-matrix:
-  exclude:
-    - python: "3.3"
-      env: UNCERTAINTIES="Y" NUMPY_VERSION=1.6.2
-    - python: "3.4"
-      env: UNCERTAINTIES="Y" NUMPY_VERSION=1.6.2
-    - python: "3.4"
-      env: UNCERTAINTIES="Y" NUMPY_VERSION=1.7.1
-    - python: "3.3"
-      env: UNCERTAINTIES="N" NUMPY_VERSION=1.6.2
-    - python: "3.4"
-      env: UNCERTAINTIES="N" NUMPY_VERSION=1.6.2
-    - python: "3.4"
-      env: UNCERTAINTIES="N" NUMPY_VERSION=1.7.1
 
=== modified file 'AUTHORS'
--- AUTHORS	2014-09-05 23:26:05 +0000
+++ AUTHORS	2015-01-07 15:51:38 +0000
@@ -5,9 +5,9 @@
 * Alexander Böhn <[e-mail]>
 * Brend Wanders <[e-mail]>
 * choloepus
-* coutinho <[e-mail]>
 * Daniel Sokolowski <[e-mail]>
 * Dave Brooks <[e-mail]>
+* David Linke
 * Eduard Bopp <[e-mail]>
 * Felix Hummel <[e-mail]>
 * Giel van Schijndel <[e-mail]>
@@ -15,11 +15,17 @@
 * Jim Turner <[e-mail]>
 * Joel B. Mohler <[e-mail]>
 * John David Reaver <[e-mail]>
+* Jonas Olson <[e-mail]>
 * Kenneth D. Mankoff <[e-mail]>
 * Luke Campbell <[e-mail]>
+* Matthieu Dartiailh <[e-mail]>
 * Nate Bogdanowicz <[e-mail]>
 * Peter Grayson <[e-mail]>
 * Richard Barnes <[e-mail]>
+* Ryan Kingsbury <[e-mail]>
 * Sundar Raman <[e-mail]>
 * Tiago Coutinho <[e-mail]>
 * Tom Ritchford <[e-mail]>
+* Virgil Dupras <[e-mail]>
+
+(If you think that your name belongs here, please let the maintainer know)
 
=== modified file 'CHANGES'
--- CHANGES	2014-09-05 23:26:05 +0000
+++ CHANGES	2015-01-07 15:51:38 +0000
@@ -2,6 +2,39 @@
 ==============
 
 
+0.6 (2014-11-07)
+----------------
+
+- Fix operations with measurments and user defined units.
+  (Issue #204)
+- Faster conversions through caching and other performance improvements.
+  (Issue #193, thanks MatthieuDartiailh)
+- Better error messages on Quantity.__setitem__.
+  (Issue #191)
+- Fixed abbreviation of fluid_ounce.
+  (Issue #187, thanks hsoft)
+- Defined Angstrom symbol.
+  (Issue #181, thanks JonasOlson)
+- Removed fetching version from git repo as it triggers XCode installation on OSX.
+  (Issue #178, thanks deanishe)
+- Improved context documentation.
+  (Issue #176 and 179, thanks rsking84)
+- Added Chemistry context.
+  (Issue #179, thanks rsking84)
+- Fix help(UnitRegisty)
+  (Issue #168)
+- Optimized "get_dimensionality" and "get_base_name".
+  (Issue #166 and #167, thanks jbmohler)
+- Renamed ureg.parse_units parameter "to_delta" to "as_delta" to make clear.
+  that no conversion happens. Accordingly, the parameter/property
+  "default_to_delta" of UnitRegistry was renamed to "default_as_delta".
+  (Issue #158, thanks dalit)
+- Fixed problem when adding two uncertainties.
+  (thanks dalito)
+- Full support for Offset units (e.g. temperature)
+  (Issue #88, #143, #147 and #161, thanks dalito)
+
+
 0.5.2 (2014-07-31)
 ------------------
 
 
=== added file 'CHANGES_DEV'
--- CHANGES_DEV	1970-01-01 00:00:00 +0000
+++ CHANGES_DEV	2015-01-07 15:51:38 +0000
@@ -0,0 +1,5 @@
+
+
+
+0.7 (unreleased)
+----------------
 
=== modified file 'MANIFEST.in'
--- MANIFEST.in	2014-09-05 23:26:05 +0000
+++ MANIFEST.in	2015-01-07 15:51:38 +0000
@@ -1,4 +1,4 @@
-include README AUTHORS CHANGES LICENSE
+include README AUTHORS CHANGES LICENSE CHANGES_DEV
 recursive-include pint *
 recursive-include docs *
 recursive-include bench *
 
=== added file 'PKG-INFO'
--- PKG-INFO	1970-01-01 00:00:00 +0000
+++ PKG-INFO	2015-01-07 15:51:38 +0000
@@ -0,0 +1,400 @@
+Metadata-Version: 1.1
+Name: Pint
+Version: 0.6
+Summary: Physical quantities module
+Home-page: https://github.com/hgrecco/pint
+Author: Hernan E. Grecco
+Author-email: [e-mail]
+License: BSD
+Description: Pint: a Python units library
+        ============================
+        
+        Pint is Python module/package to define, operate and manipulate physical
+        quantities: the product of a numerical value and a unit of measurement.
+        It allows arithmetic operations between them and conversions from and
+        to different units.
+        
+        It is distributed with a comprehensive list of physical units, prefixes
+        and constants. Due to its modular design, you to extend (or even rewrite!)
+        the complete list without changing the source code.
+        
+        It has a complete test coverage. It runs in Python 2.7 and 3.X
+        with no other dependency. It licensed under BSD.
+        
+        
+        Design principles
+        -----------------
+        
+        Although there are already a few very good Python packages to handle physical
+        quantities, no one was really fitting my needs. Like most developers, I programed
+        Pint to scratch my own itches.
+        
+        - Unit parsing: prefixed and pluralized forms of units are recognized without
+          explicitly defining them. In other words: as the prefix *kilo* and the unit *meter*
+          are defined, Pint understands *kilometers*. This results in a much shorter and
+          maintainable unit definition list as compared to other packages.
+        
+        - Standalone unit definitions: units definitions are loaded from simple and
+          easy to edit text file. Adding and changing units and their definitions does
+          not involve changing the code.
+        
+        - Advanced string formatting: a quantity can be formatted into string using
+          PEP 3101 syntax. Extended conversion flags are given to provide latex and pretty
+          formatting.
+        
+        - Small codebase: small and easy to maintain with a flat hierarchy.
+        
+        - Dependency free: it depends only on Python and its standard library.
+        
+        - Python 2 and 3: A single codebase that runs unchanged in Python 2.7+ and Python 3.0+.
+        
+        - Advanced NumPy support: While NumPy is not a requirement for Pint,
+          when available ndarray methods and ufuncs can be used in Quantity objects.
+        
+        
+        Pint is written and maintained by Hernan E. Grecco <[e-mail]>.
+        
+        Other contributors, listed alphabetically, are:
+        
+        * Alexander Böhn <[e-mail]>
+        * Brend Wanders <[e-mail]>
+        * choloepus
+        * Daniel Sokolowski <[e-mail]>
+        * Dave Brooks <[e-mail]>
+        * David Linke
+        * Eduard Bopp <[e-mail]>
+        * Felix Hummel <[e-mail]>
+        * Giel van Schijndel <[e-mail]>
+        * James Rowe <[e-mail]>
+        * Jim Turner <[e-mail]>
+        * Joel B. Mohler <[e-mail]>
+        * John David Reaver <[e-mail]>
+        * Jonas Olson <[e-mail]>
+        * Kenneth D. Mankoff <[e-mail]>
+        * Luke Campbell <[e-mail]>
+        * Matthieu Dartiailh <[e-mail]>
+        * Nate Bogdanowicz <[e-mail]>
+        * Peter Grayson <[e-mail]>
+        * Richard Barnes <[e-mail]>
+        * Ryan Kingsbury <[e-mail]>
+        * Sundar Raman <[e-mail]>
+        * Tiago Coutinho <[e-mail]>
+        * Tom Ritchford <[e-mail]>
+        * Virgil Dupras <[e-mail]>
+        
+        (If you think that your name belongs here, please let the maintainer know)
+        
+        
+        Pint Changelog
+        ==============
+        
+        
+        0.6 (2014-11-07)
+        ----------------
+        
+        - Fix operations with measurments and user defined units.
+          (Issue #204)
+        - Faster conversions through caching and other performance improvements.
+          (Issue #193, thanks MatthieuDartiailh)
+        - Better error messages on Quantity.__setitem__.
+          (Issue #191)
+        - Fixed abbreviation of fluid_ounce.
+          (Issue #187, thanks hsoft)
+        - Defined Angstrom symbol.
+          (Issue #181, thanks JonasOlson)
+        - Removed fetching version from git repo as it triggers XCode installation on OSX.
+          (Issue #178, thanks deanishe)
+        - Improved context documentation.
+          (Issue #176 and 179, thanks rsking84)
+        - Added Chemistry context.
+          (Issue #179, thanks rsking84)
+        - Fix help(UnitRegisty)
+          (Issue #168)
+        - Optimized "get_dimensionality" and "get_base_name".
+          (Issue #166 and #167, thanks jbmohler)
+        - Renamed ureg.parse_units parameter "to_delta" to "as_delta" to make clear.
+          that no conversion happens. Accordingly, the parameter/property
+          "default_to_delta" of UnitRegistry was renamed to "default_as_delta".
+          (Issue #158, thanks dalit)
+        - Fixed problem when adding two uncertainties.
+          (thanks dalito)
+        - Full support for Offset units (e.g. temperature)
+          (Issue #88, #143, #147 and #161, thanks dalito)
+        
+        
+        0.5.2 (2014-07-31)
+        ------------------
+        
+        - Changed travis config to use miniconda for faster testing.
+        - Added wheel configuration to setup.cfg.
+        - Ensure resource streams are closed after reading.
+        - Require setuptools.
+          (Issue #169)
+        - Implemented real, imag and T Quantity properties.
+          (Issue #171)
+        - Implemented __int__ and __long__ for Quantity
+          (Issue #170)
+        - Fixed SI prefix error on ureg.convert.
+          (Issue #156, thanks jdreaver)
+        - Fixed parsing of multiparemeter contexts.
+          (Issue #174)
+        
+        
+        0.5.1 (2014-06-03)
+        ------------------
+        
+        - Implemented a standard way to change the registry used in unpickling operations.
+          (Issue #148)
+        - Fix bug where conversion would fail due to caching.
+          (Issue #140, thanks jdreaver)
+        - Allow assigning Not a Number to a quantity array.
+          (Issue #127)
+        - Decoupled Quantity in place and not in place unit conversion methods.
+        - Return None in functions that modify quantities in place.
+        - Improved testing infrastructure to check for unwanted warnings.
+        - Added test function at the package level to run all tests.
+        
+        
+        0.5 (2014-05-07)
+        ----------------
+        
+        - Improved test suite helper functions.
+        - Print honors default format w/o format().
+          (Issue #132, thanks mankoff)
+        - Fixed sum() by treating number zero as a special case.
+          (Issue #122, thanks rec)
+        - Improved behaviour in ScaleConverter, OffsetConverter and Quantity.to.
+          (Issue #120)
+        - Reimplemented loading of default definitions to allow Pint in a cx_freeze or similar package.
+          (Issue #118, thanks jbmohler)
+        - Implemented parsing of pretty printed units.
+          (Issue #117, thanks jpgrayson)
+        - Fixed representation of dimensionless quantities.
+          (Issue #112, thanks rec)
+        - Raise error when invalid formatting code is given.
+          (Issue #111, thanks rec)
+        - Default registry to lazy load, raise error on redefinition
+          (Issue #108, thanks rec, aepsil0n)
+        - Added condensed format.
+          (Issue #107, thanks rec)
+        - Added UnitRegistry () operator to parse expression replacing [].
+          (Issue #106, thanks rec)
+        - Optional case insensitive unit parsing. 
+          (Issue #105, thanks rec, jeremyfreeman, dbrnz)
+        - Change the Quantity mutability depending on magnitude type.
+          (Issue #104, thanks rec)
+        - Implemented API to list compatible units.
+          (Issue #89)
+        - Implemented cache of key UnitRegistry methods.
+        - Rewrote the Measurement class to use uncertainties.
+          (Issue #24)
+        
+        
+        0.4.2 (2014-02-14)
+        ------------------
+        
+        - Python 2.6 support
+          (Issue #96, thanks tiagocoutinho)
+        - Fixed symbol for inch.
+          (Issue #102, thanks cybertoast)
+        - Stop raising AttributeError when wrapping funcs without all of the attributes.
+          (Issue #100, thanks jturner314)
+        - Fixed warning appearing in Py2.x when comparing a Numpy Array with an empty string.
+          (Issue #98, thanks jturner314)
+        - Add links to AUR packages in docs.
+          (Issue #91, thanks jturner314)
+        - Fixed garbage collection related problem.
+          (Issue #92, thanks jturner314)
+        
+        
+        0.4.1 (2014-01-12)
+        ------------------
+        
+        - Integer Division with Arrays.
+          (Issue #80, thanks jdreaver)
+        - Improved Documentation.
+          (Issue #83, thanks choloepus)
+        - Removed 'h' alias for hour due to conflict with Planck's constant.
+          (Issue #82, thanks choloepus)
+        - Improved get_base_units for non-multiplicative units.
+          (Issue #85, thanks exxus)
+        - Refactored code for multiplication.
+          (Issue #84, thanks jturner314)
+        - Removed 'R' alias for roentgen as it collides with molar_gas_constant.
+          (Issue #87, thanks rsking84)
+        - Improved naming of temperature units and multiplication of non-multiplicative units.
+          (Issue #86, tahsnk exxus)
+        
+        
+        
+        0.4 (2013-12-17)
+        ----------------
+        
+        - Introduced Contexts: relation between incompatible dimensions.
+          (Issue #65)
+        - Fixed get_base_units for non multiplicative units.
+          (Related to issue #66)
+        - Implemented default formatting for quantities.
+        - Changed comparison between Quantities containing NumPy arrays.
+          (Issue #75) - BACKWARDS INCOMPATIBLE CHANGE
+        - Fixes for NumPy 1.8 due to changes in handling binary ops.
+          (Issue #73)
+        
+        
+        0.3.3 (2013-11-29)
+        ------------------
+        
+        - ParseHelper can now parse units named like python keywords.
+          (Issue #69)
+        - Fix comparison of quantities.
+          (Issue #74)
+        - Fix Inequality operator.
+          (Issue #70, thanks muggenhor)
+        - Improved travis configuration.
+          (thanks muggenhor)
+        
+        
+        0.3.2 (2013-10-22)
+        ------------------
+        
+        - Fix get_dimensionality for non multiplicative units.
+          (Issue #66)
+        - Proper handling of @import directive inside a file read using pkg_resources.
+          (Issue #68)
+        
+        
+        0.3.1 (2013-09-15)
+        ------------------
+        
+        - fix right division on python 2.7
+          (Issue #58, thanks natezb)
+        - fix formatting of fractional exponentials between 0 and 1.
+          (Issue #62, thanks jdreaver)
+        - fix installation as egg.
+          (Issue #61)
+        - fix handling of strange values as input of Quantity.
+          (Issue #53)
+        - math operations between quantities of different registries now raise a ValueError.
+          (Issue #52)
+        
+        
+        0.3 (2013-09-02)
+        ----------------
+        
+        - support for IPython autocomplete and rich display.
+          (Issues #30 and #31)
+        - support for @import directive in definitions file.
+          (Issue #22)
+        - support for wrapping functions to make them pint-aware.
+          (Issue #16)
+        - support for comparing UnitsContainer to string.
+          (Issue #35)
+        - fix error raised while converting from a single unit to one expressed as
+          the relation between many.
+          (Issue #29)
+        - fix error raised when unit symbol is missing.
+          (Issue #41)
+        - fix error raised when magnitude is Decimal.
+          (Issue #46, thanks danielsokolowski)
+        - support for non-installed pint.
+          (Issue #42, thanks danielsokolowski)
+        - support for application of numpy function on non-ndarray magnitudes.
+          (Issue #44)
+        - support for math operations on dimensionless Quantities (written with units).
+          (Issue #45)
+        - fix obtaining dimensionless quantity from string.
+          (Issue #50)
+        - fix adding and comparing numbers to a dimensionless quantity (written with units).
+          (Issue #54)
+        - Support for iter in Quantity.
+          (Issue #55, thanks natezb)
+        
+        
+        0.2.1 (2013-07-02)
+        ------------------
+        
+        - fix error raised while converting from a single unit to one expressed as
+          the relation between many.
+          (Issue #29)
+        
+        
+        0.2 (2013-05-13)
+        ----------------
+        
+        - support for Measurement (Quantity +/- error).
+        - implemented buckingham pi theorem for dimensional analysis.
+        - support for temperature units and temperature difference units.
+        - parser can infers if the user mean temperature or temperature difference.
+        - support for derived dimensions (e.g. [speed] = [length] / [time]).
+        - refactored the code into multiple files.
+        - refactored code to isolate definitions and converters.
+        - refactored formatter out of UnitParser class.
+        - added tox and travis config files for CI.
+        - comprehensive NumPy testing including almost all ufuncs.
+        - full NumPy support (features is not longer experimental).
+        - fixed bug preventing from having independent registries.
+          (Issue #10, thanks bwanders)
+        - forces real division as default for Quantities.
+          (Issue #7, thanks dbrnz)
+        - improved default unit definition file.
+          (Issue #13, thanks r-barnes)
+        - smarter parser supporting spaces as multiplications and other nice features.
+          (Issue #13, thanks r-barnes)
+        - moved testsuite inside package.
+        - short forms of binary prefixes, more units and fix to less than comparison.
+          (Issue #20, thanks muggenhor)
+        - pint is now zip-safe
+          (Issue #23, thanks muggenhor)
+        
+        
+        Version 0.1.3 (2013-01-07)
+        --------------------------
+        
+        - abbreviated quantity string formating.
+        - complete Python 2.7 compatibility.
+        - implemented pickle support for Quantities objects.
+        - extended NumPy support.
+        - various bugfixes.
+        
+        
+        Version 0.1.2 (2012-08-12)
+        --------------------------
+        
+        - experimenal NumPy support.
+        - included default unit definitions file.
+          (Issue #1, thanks fish2000)
+        - better testing.
+        - various bugfixes.
+        - fixed some units definitions.
+          (Issue #4, thanks craigholm)
+        
+        
+        Version 0.1.1 (2012-07-31)
+        --------------------------
+        
+        - better packaging and installation.
+        
+        
+        Version 0.1   (2012-07-26)
+        --------------------------
+        
+        - first public release.
+        
+Keywords: physical quantities unit conversion science
+Platform: UNKNOWN
+Classifier: Development Status :: 4 - Beta
+Classifier: Intended Audience :: Developers
+Classifier: Intended Audience :: Science/Research
+Classifier: License :: OSI Approved :: BSD License
+Classifier: Operating System :: MacOS :: MacOS X
+Classifier: Operating System :: Microsoft :: Windows
+Classifier: Operating System :: POSIX
+Classifier: Programming Language :: Python
+Classifier: Topic :: Scientific/Engineering
+Classifier: Topic :: Software Development :: Libraries
+Classifier: Programming Language :: Python :: 2.6
+Classifier: Programming Language :: Python :: 2.7
+Classifier: Programming Language :: Python :: 3.0
+Classifier: Programming Language :: Python :: 3.1
+Classifier: Programming Language :: Python :: 3.2
+Classifier: Programming Language :: Python :: 3.3
 
=== added directory 'Pint.egg-info'
=== added file 'Pint.egg-info/PKG-INFO'
--- Pint.egg-info/PKG-INFO	1970-01-01 00:00:00 +0000
+++ Pint.egg-info/PKG-INFO	2015-01-07 15:51:38 +0000
@@ -0,0 +1,400 @@
+Metadata-Version: 1.1
+Name: Pint
+Version: 0.6
+Summary: Physical quantities module
+Home-page: https://github.com/hgrecco/pint
+Author: Hernan E. Grecco
+Author-email: [e-mail]
+License: BSD
+Description: Pint: a Python units library
+        ============================
+        
+        Pint is Python module/package to define, operate and manipulate physical
+        quantities: the product of a numerical value and a unit of measurement.
+        It allows arithmetic operations between them and conversions from and
+        to different units.
+        
+        It is distributed with a comprehensive list of physical units, prefixes
+        and constants. Due to its modular design, you to extend (or even rewrite!)
+        the complete list without changing the source code.
+        
+        It has a complete test coverage. It runs in Python 2.7 and 3.X
+        with no other dependency. It licensed under BSD.
+        
+        
+        Design principles
+        -----------------
+        
+        Although there are already a few very good Python packages to handle physical
+        quantities, no one was really fitting my needs. Like most developers, I programed
+        Pint to scratch my own itches.
+        
+        - Unit parsing: prefixed and pluralized forms of units are recognized without
+          explicitly defining them. In other words: as the prefix *kilo* and the unit *meter*
+          are defined, Pint understands *kilometers*. This results in a much shorter and
+          maintainable unit definition list as compared to other packages.
+        
+        - Standalone unit definitions: units definitions are loaded from simple and
+          easy to edit text file. Adding and changing units and their definitions does
+          not involve changing the code.
+        
+        - Advanced string formatting: a quantity can be formatted into string using
+          PEP 3101 syntax. Extended conversion flags are given to provide latex and pretty
+          formatting.
+        
+        - Small codebase: small and easy to maintain with a flat hierarchy.
+        
+        - Dependency free: it depends only on Python and its standard library.
+        
+        - Python 2 and 3: A single codebase that runs unchanged in Python 2.7+ and Python 3.0+.
+        
+        - Advanced NumPy support: While NumPy is not a requirement for Pint,
+          when available ndarray methods and ufuncs can be used in Quantity objects.
+        
+        
+        Pint is written and maintained by Hernan E. Grecco <[e-mail]>.
+        
+        Other contributors, listed alphabetically, are:
+        
+        * Alexander Böhn <[e-mail]>
+        * Brend Wanders <[e-mail]>
+        * choloepus
+        * Daniel Sokolowski <[e-mail]>
+        * Dave Brooks <[e-mail]>
+        * David Linke
+        * Eduard Bopp <[e-mail]>
+        * Felix Hummel <[e-mail]>
+        * Giel van Schijndel <[e-mail]>
+        * James Rowe <[e-mail]>
+        * Jim Turner <[e-mail]>
+        * Joel B. Mohler <[e-mail]>
+        * John David Reaver <[e-mail]>
+        * Jonas Olson <[e-mail]>
+        * Kenneth D. Mankoff <[e-mail]>
+        * Luke Campbell <[e-mail]>
+        * Matthieu Dartiailh <[e-mail]>
+        * Nate Bogdanowicz <[e-mail]>
+        * Peter Grayson <[e-mail]>
+        * Richard Barnes <[e-mail]>
+        * Ryan Kingsbury <[e-mail]>
+        * Sundar Raman <[e-mail]>
+        * Tiago Coutinho <[e-mail]>
+        * Tom Ritchford <[e-mail]>
+        * Virgil Dupras <[e-mail]>
+        
+        (If you think that your name belongs here, please let the maintainer know)
+        
+        
+        Pint Changelog
+        ==============
+        
+        
+        0.6 (2014-11-07)
+        ----------------
+        
+        - Fix operations with measurments and user defined units.
+          (Issue #204)
+        - Faster conversions through caching and other performance improvements.
+          (Issue #193, thanks MatthieuDartiailh)
+        - Better error messages on Quantity.__setitem__.
+          (Issue #191)
+        - Fixed abbreviation of fluid_ounce.
+          (Issue #187, thanks hsoft)
+        - Defined Angstrom symbol.
+          (Issue #181, thanks JonasOlson)
+        - Removed fetching version from git repo as it triggers XCode installation on OSX.
+          (Issue #178, thanks deanishe)
+        - Improved context documentation.
+          (Issue #176 and 179, thanks rsking84)
+        - Added Chemistry context.
+          (Issue #179, thanks rsking84)
+        - Fix help(UnitRegisty)
+          (Issue #168)
+        - Optimized "get_dimensionality" and "get_base_name".
+          (Issue #166 and #167, thanks jbmohler)
+        - Renamed ureg.parse_units parameter "to_delta" to "as_delta" to make clear.
+          that no conversion happens. Accordingly, the parameter/property
+          "default_to_delta" of UnitRegistry was renamed to "default_as_delta".
+          (Issue #158, thanks dalit)
+        - Fixed problem when adding two uncertainties.
+          (thanks dalito)
+        - Full support for Offset units (e.g. temperature)
+          (Issue #88, #143, #147 and #161, thanks dalito)
+        
+        
+        0.5.2 (2014-07-31)
+        ------------------
+        
+        - Changed travis config to use miniconda for faster testing.
+        - Added wheel configuration to setup.cfg.
+        - Ensure resource streams are closed after reading.
+        - Require setuptools.
+          (Issue #169)
+        - Implemented real, imag and T Quantity properties.
+          (Issue #171)
+        - Implemented __int__ and __long__ for Quantity
+          (Issue #170)
+        - Fixed SI prefix error on ureg.convert.
+          (Issue #156, thanks jdreaver)
+        - Fixed parsing of multiparemeter contexts.
+          (Issue #174)
+        
+        
+        0.5.1 (2014-06-03)
+        ------------------
+        
+        - Implemented a standard way to change the registry used in unpickling operations.
+          (Issue #148)
+        - Fix bug where conversion would fail due to caching.
+          (Issue #140, thanks jdreaver)
+        - Allow assigning Not a Number to a quantity array.
+          (Issue #127)
+        - Decoupled Quantity in place and not in place unit conversion methods.
+        - Return None in functions that modify quantities in place.
+        - Improved testing infrastructure to check for unwanted warnings.
+        - Added test function at the package level to run all tests.
+        
+        
+        0.5 (2014-05-07)
+        ----------------
+        
+        - Improved test suite helper functions.
+        - Print honors default format w/o format().
+          (Issue #132, thanks mankoff)
+        - Fixed sum() by treating number zero as a special case.
+          (Issue #122, thanks rec)
+        - Improved behaviour in ScaleConverter, OffsetConverter and Quantity.to.
+          (Issue #120)
+        - Reimplemented loading of default definitions to allow Pint in a cx_freeze or similar package.
+          (Issue #118, thanks jbmohler)
+        - Implemented parsing of pretty printed units.
+          (Issue #117, thanks jpgrayson)
+        - Fixed representation of dimensionless quantities.
+          (Issue #112, thanks rec)
+        - Raise error when invalid formatting code is given.
+          (Issue #111, thanks rec)
+        - Default registry to lazy load, raise error on redefinition
+          (Issue #108, thanks rec, aepsil0n)
+        - Added condensed format.
+          (Issue #107, thanks rec)
+        - Added UnitRegistry () operator to parse expression replacing [].
+          (Issue #106, thanks rec)
+        - Optional case insensitive unit parsing. 
+          (Issue #105, thanks rec, jeremyfreeman, dbrnz)
+        - Change the Quantity mutability depending on magnitude type.
+          (Issue #104, thanks rec)
+        - Implemented API to list compatible units.
+          (Issue #89)
+        - Implemented cache of key UnitRegistry methods.
+        - Rewrote the Measurement class to use uncertainties.
+          (Issue #24)
+        
+        
+        0.4.2 (2014-02-14)
+        ------------------
+        
+        - Python 2.6 support
+          (Issue #96, thanks tiagocoutinho)
+        - Fixed symbol for inch.
+          (Issue #102, thanks cybertoast)
+        - Stop raising AttributeError when wrapping funcs without all of the attributes.
+          (Issue #100, thanks jturner314)
+        - Fixed warning appearing in Py2.x when comparing a Numpy Array with an empty string.
+          (Issue #98, thanks jturner314)
+        - Add links to AUR packages in docs.
+          (Issue #91, thanks jturner314)
+        - Fixed garbage collection related problem.
+          (Issue #92, thanks jturner314)
+        
+        
+        0.4.1 (2014-01-12)
+        ------------------
+        
+        - Integer Division with Arrays.
+          (Issue #80, thanks jdreaver)
+        - Improved Documentation.
+          (Issue #83, thanks choloepus)
+        - Removed 'h' alias for hour due to conflict with Planck's constant.
+          (Issue #82, thanks choloepus)
+        - Improved get_base_units for non-multiplicative units.
+          (Issue #85, thanks exxus)
+        - Refactored code for multiplication.
+          (Issue #84, thanks jturner314)
+        - Removed 'R' alias for roentgen as it collides with molar_gas_constant.
+          (Issue #87, thanks rsking84)
+        - Improved naming of temperature units and multiplication of non-multiplicative units.
+          (Issue #86, tahsnk exxus)
+        
+        
+        
+        0.4 (2013-12-17)
+        ----------------
+        
+        - Introduced Contexts: relation between incompatible dimensions.
+          (Issue #65)
+        - Fixed get_base_units for non multiplicative units.
+          (Related to issue #66)
+        - Implemented default formatting for quantities.
+        - Changed comparison between Quantities containing NumPy arrays.
+          (Issue #75) - BACKWARDS INCOMPATIBLE CHANGE
+        - Fixes for NumPy 1.8 due to changes in handling binary ops.
+          (Issue #73)
+        
+        
+        0.3.3 (2013-11-29)
+        ------------------
+        
+        - ParseHelper can now parse units named like python keywords.
+          (Issue #69)
+        - Fix comparison of quantities.
+          (Issue #74)
+        - Fix Inequality operator.
+          (Issue #70, thanks muggenhor)
+        - Improved travis configuration.
+          (thanks muggenhor)
+        
+        
+        0.3.2 (2013-10-22)
+        ------------------
+        
+        - Fix get_dimensionality for non multiplicative units.
+          (Issue #66)
+        - Proper handling of @import directive inside a file read using pkg_resources.
+          (Issue #68)
+        
+        
+        0.3.1 (2013-09-15)
+        ------------------
+        
+        - fix right division on python 2.7
+          (Issue #58, thanks natezb)
+        - fix formatting of fractional exponentials between 0 and 1.
+          (Issue #62, thanks jdreaver)
+        - fix installation as egg.
+          (Issue #61)
+        - fix handling of strange values as input of Quantity.
+          (Issue #53)
+        - math operations between quantities of different registries now raise a ValueError.
+          (Issue #52)
+        
+        
+        0.3 (2013-09-02)
+        ----------------
+        
+        - support for IPython autocomplete and rich display.
+          (Issues #30 and #31)
+        - support for @import directive in definitions file.
+          (Issue #22)
+        - support for wrapping functions to make them pint-aware.
+          (Issue #16)
+        - support for comparing UnitsContainer to string.
+          (Issue #35)
+        - fix error raised while converting from a single unit to one expressed as
+          the relation between many.
+          (Issue #29)
+        - fix error raised when unit symbol is missing.
+          (Issue #41)
+        - fix error raised when magnitude is Decimal.
+          (Issue #46, thanks danielsokolowski)
+        - support for non-installed pint.
+          (Issue #42, thanks danielsokolowski)
+        - support for application of numpy function on non-ndarray magnitudes.
+          (Issue #44)
+        - support for math operations on dimensionless Quantities (written with units).
+          (Issue #45)
+        - fix obtaining dimensionless quantity from string.
+          (Issue #50)
+        - fix adding and comparing numbers to a dimensionless quantity (written with units).
+          (Issue #54)
+        - Support for iter in Quantity.
+          (Issue #55, thanks natezb)
+        
+        
+        0.2.1 (2013-07-02)
+        ------------------
+        
+        - fix error raised while converting from a single unit to one expressed as
+          the relation between many.
+          (Issue #29)
+        
+        
+        0.2 (2013-05-13)
+        ----------------
+        
+        - support for Measurement (Quantity +/- error).
+        - implemented buckingham pi theorem for dimensional analysis.
+        - support for temperature units and temperature difference units.
+        - parser can infers if the user mean temperature or temperature difference.
+        - support for derived dimensions (e.g. [speed] = [length] / [time]).
+        - refactored the code into multiple files.
+        - refactored code to isolate definitions and converters.
+        - refactored formatter out of UnitParser class.
+        - added tox and travis config files for CI.
+        - comprehensive NumPy testing including almost all ufuncs.
+        - full NumPy support (features is not longer experimental).
+        - fixed bug preventing from having independent registries.
+          (Issue #10, thanks bwanders)
+        - forces real division as default for Quantities.
+          (Issue #7, thanks dbrnz)
+        - improved default unit definition file.
+          (Issue #13, thanks r-barnes)
+        - smarter parser supporting spaces as multiplications and other nice features.
+          (Issue #13, thanks r-barnes)
+        - moved testsuite inside package.
+        - short forms of binary prefixes, more units and fix to less than comparison.
+          (Issue #20, thanks muggenhor)
+        - pint is now zip-safe
+          (Issue #23, thanks muggenhor)
+        
+        
+        Version 0.1.3 (2013-01-07)
+        --------------------------
+        
+        - abbreviated quantity string formating.
+        - complete Python 2.7 compatibility.
+        - implemented pickle support for Quantities objects.
+        - extended NumPy support.
+        - various bugfixes.
+        
+        
+        Version 0.1.2 (2012-08-12)
+        --------------------------
+        
+        - experimenal NumPy support.
+        - included default unit definitions file.
+          (Issue #1, thanks fish2000)
+        - better testing.
+        - various bugfixes.
+        - fixed some units definitions.
+          (Issue #4, thanks craigholm)
+        
+        
+        Version 0.1.1 (2012-07-31)
+        --------------------------
+        
+        - better packaging and installation.
+        
+        
+        Version 0.1   (2012-07-26)
+        --------------------------
+        
+        - first public release.
+        
+Keywords: physical quantities unit conversion science
+Platform: UNKNOWN
+Classifier: Development Status :: 4 - Beta
+Classifier: Intended Audience :: Developers
+Classifier: Intended Audience :: Science/Research
+Classifier: License :: OSI Approved :: BSD License
+Classifier: Operating System :: MacOS :: MacOS X
+Classifier: Operating System :: Microsoft :: Windows
+Classifier: Operating System :: POSIX
+Classifier: Programming Language :: Python
+Classifier: Topic :: Scientific/Engineering
+Classifier: Topic :: Software Development :: Libraries
+Classifier: Programming Language :: Python :: 2.6
+Classifier: Programming Language :: Python :: 2.7
+Classifier: Programming Language :: Python :: 3.0
+Classifier: Programming Language :: Python :: 3.1
+Classifier: Programming Language :: Python :: 3.2
+Classifier: Programming Language :: Python :: 3.3
 
=== added file 'Pint.egg-info/SOURCES.txt'
--- Pint.egg-info/SOURCES.txt	1970-01-01 00:00:00 +0000
+++ Pint.egg-info/SOURCES.txt	2015-01-07 15:51:38 +0000
@@ -0,0 +1,72 @@
+AUTHORS
+CHANGES
+CHANGES_DEV
+LICENSE
+MANIFEST.in
+README
+setup.cfg
+setup.py
+Pint.egg-info/PKG-INFO
+Pint.egg-info/SOURCES.txt
+Pint.egg-info/dependency_links.txt
+Pint.egg-info/entry_points.txt
+Pint.egg-info/top_level.txt
+Pint.egg-info/zip-safe
+bench/bench.py
+bench/bench_base.yaml
+bench/bench_numpy.yaml
+docs/Makefile
+docs/conf.py
+docs/contexts.rst
+docs/contributing.rst
+docs/defining.rst
+docs/faq.rst
+docs/getting.rst
+docs/index.rst
+docs/make.bat
+docs/measurement.rst
+docs/nonmult.rst
+docs/numpy.rst
+docs/pitheorem.rst
+docs/serialization.rst
+docs/tutorial.rst
+docs/wrapping.rst
+docs/_static/logo-full.jpg
+docs/_templates/sidebarintro.html
+docs/_templates/sidebarlogo.html
+docs/_themes/.gitignore
+docs/_themes/LICENSE
+docs/_themes/README
+docs/_themes/flask_theme_support.py
+docs/_themes/flask/layout.html
+docs/_themes/flask/relations.html
+docs/_themes/flask/theme.conf
+docs/_themes/flask/static/flasky.css_t
+docs/_themes/flask/static/small_flask.css
+pint/__init__.py
+pint/constants_en.txt
+pint/context.py
+pint/default_en.txt
+pint/formatting.py
+pint/measurement.py
+pint/quantity.py
+pint/unit.py
+pint/util.py
+pint/compat/__init__.py
+pint/compat/chainmap.py
+pint/compat/lrucache.py
+pint/compat/nullhandler.py
+pint/compat/transformdict.py
+pint/testsuite/__init__.py
+pint/testsuite/helpers.py
+pint/testsuite/parameterized.py
+pint/testsuite/test_contexts.py
+pint/testsuite/test_formatter.py
+pint/testsuite/test_issues.py
+pint/testsuite/test_measurement.py
+pint/testsuite/test_numpy.py
+pint/testsuite/test_pitheorem.py
+pint/testsuite/test_quantity.py
+pint/testsuite/test_umath.py
+pint/testsuite/test_unit.py
+pint/testsuite/test_util.py
 \ No newline at end of file
 
=== added file 'Pint.egg-info/dependency_links.txt'
--- Pint.egg-info/dependency_links.txt	1970-01-01 00:00:00 +0000
+++ Pint.egg-info/dependency_links.txt	2015-01-07 15:51:38 +0000
@@ -0,0 +1,1 @@
+
 
=== added file 'Pint.egg-info/entry_points.txt'
--- Pint.egg-info/entry_points.txt	1970-01-01 00:00:00 +0000
+++ Pint.egg-info/entry_points.txt	2015-01-07 15:51:38 +0000
@@ -0,0 +1,3 @@
+[zest.releaser.releaser.after_checkout]
+pyroma = pint:_run_pyroma
+
 
=== added file 'Pint.egg-info/top_level.txt'
--- Pint.egg-info/top_level.txt	1970-01-01 00:00:00 +0000
+++ Pint.egg-info/top_level.txt	2015-01-07 15:51:38 +0000
@@ -0,0 +1,1 @@
+pint
 
=== added file 'Pint.egg-info/zip-safe'
--- Pint.egg-info/zip-safe	1970-01-01 00:00:00 +0000
+++ Pint.egg-info/zip-safe	2015-01-07 15:51:38 +0000
@@ -0,0 +1,1 @@
+
 
=== modified file 'debian/changelog'
--- debian/changelog	2014-09-05 23:26:05 +0000
+++ debian/changelog	2015-01-07 15:51:38 +0000
@@ -1,3 +1,10 @@
+python-pint (0.6-0ubuntu1) UNRELEASED; urgency=medium
+
+  * New upstream release.
+  * d/control: Add python-numpy and python3-numpy to Build-Depends.
+
+ -- Corey Bryant <[e-mail]>  Wed, 07 Jan 2015 10:47:04 -0500
+
 python-pint (0.5.2-1) unstable; urgency=medium
 
   * Initial release. (Closes: #760586)
 
=== modified file 'debian/control'
--- debian/control	2014-09-05 23:26:05 +0000
+++ debian/control	2015-01-07 15:51:38 +0000
@@ -6,11 +6,13 @@
 Build-Depends: debhelper (>= 9),
                python-all (>= 2.6.6-3~),
                python-nose,
+               python-numpy,
                python-setuptools,
                python-sphinx,
                python-yaml,
                python3-all,
                python3-nose,
+               python3-numpy,
                python3-setuptools,
                python3-yaml
 Standards-Version: 3.9.5
 
=== modified file 'debian/watch'
--- debian/watch	2014-09-05 23:26:05 +0000
+++ debian/watch	2015-01-07 15:51:38 +0000
@@ -1,3 +1,3 @@
 version=3
-http://pypi.python.org/packages/source/P/Pint Pint-(.*).tar.gz
-
+opts="uversionmangle=s/.zip//" \
+ http://pypi.python.org/packages/source/P/Pint/ Pint-(.*).zip
 
=== modified file 'docs/_themes/flask/layout.html'
--- docs/_themes/flask/layout.html	2014-09-05 23:26:05 +0000
+++ docs/_themes/flask/layout.html	2015-01-07 15:51:38 +0000
@@ -10,7 +10,7 @@
 {%- block relbar2 %}
   {% if theme_github_fork %}
     <a href="http://github.com/{{ theme_github_fork }}"><img style="position: fixed; top: 0; right: 0; border: 0;"
-    src="" alt="Fork me on GitHub" /></a>
+    src="http://s3.amazonaws.com/github/ribbons/forkme_right_darkblue_121621.png" alt="Fork me on GitHub" /></a>
   {% endif %}
 {% endblock %}
 {% block header %}
 
=== modified file 'docs/conf.py'
--- docs/conf.py	2014-09-05 23:26:05 +0000
+++ docs/conf.py	2015-01-07 15:51:38 +0000
@@ -28,7 +28,7 @@
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.autodoc', 'sphinx.ext.doctest', 'sphinx.ext.coverage', 'sphinx.ext.viewcode']
+extensions = ['sphinx.ext.autodoc', 'sphinx.ext.doctest', 'sphinx.ext.intersphinx', 'sphinx.ext.coverage', 'sphinx.ext.viewcode', 'sphinx.ext.mathjax']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
 
=== modified file 'docs/contexts.rst'
--- docs/contexts.rst	2014-09-05 23:26:05 +0000
+++ docs/contexts.rst	2015-01-07 15:51:38 +0000
@@ -108,6 +108,15 @@
     >>> f.to('nm', 'sp', n=1.33)
     <Quantity(398.496240602, 'nanometer')>
 
+Contexts can also accept Pint Quantity objects as parameters. For example, the 'chemistry' 
+context accepts the molecular weight of a substance (as a Quantity with dimensions of 
+[mass]/[substance]) to allow conversion between moles and mass.
+
+.. doctest::
+
+    >>> substance = 95 * ureg('g')
+    >>> moles = substance.to('moles', 'chemistry', mw = 5 * ureg('g/mol'))
+    <Quantity(19.0, 'mole')>
 
 
 Defining contexts in a file
@@ -129,7 +138,8 @@
 All parameters are named and default values are mandatory. Multiple parameters
 are separated by commas (like in a python function definition). Finally, you provide the name
 of the context (e.g. spectroscopy) and, optionally, a short version of the name (e.g. sp)
-separated by an equal sign.
+separated by an equal sign. See the definition of the 'chemistry' context in default_en.txt 
+for an example of a multiple-parameter context.
 
 Conversions rules are specified by providing source and destination dimensions separated
 using a colon (`:`) from the equation. A special variable named `value` will be replaced
@@ -140,6 +150,8 @@
 from the first dimension to the second one. A double arrow (`<->`) is used to
 indicate that the transformation operates both ways.
 
+Context definitions are stored and imported exactly like custom units definition file 
+(and can be included in the same file as unit definitions). See "Defining units" for details.
 
 Defining contexts programmatically
 ----------------------------------
 
=== modified file 'docs/faq.rst'
--- docs/faq.rst	2014-09-05 23:26:05 +0000
+++ docs/faq.rst	2015-01-07 15:51:38 +0000
@@ -13,6 +13,8 @@
 You mention other similar Python libraries. Can you point me to those?
 ----------------------------------------------------------------------
 
+`natu <http://kdavies4.github.io/natu/>`_
+
 `Buckingham <https://code.google.com/p/buckingham/>`_
 
 `Magnitude <http://github.com/juanre/magnitude.git>`_
 
=== modified file 'docs/index.rst'
--- docs/index.rst	2014-09-05 23:26:05 +0000
+++ docs/index.rst	2015-01-07 15:51:38 +0000
@@ -9,7 +9,7 @@
 
 Pint is Python package to define, operate and manipulate **physical quantities**: the product of a numerical value and a unit of measurement. It allows arithmetic operations between them and conversions from and to different units.
 
-It is distributed with a comprehensive list of physical units, prefixes and constants. Due to its modular design, you can extend (or even rewrite!) the complete list without changing the source code.
+It is distributed with a comprehensive list of physical units, prefixes and constants. Due to its modular design, you can extend (or even rewrite!) the complete list without changing the source code. It supports a lot of numpy mathematical operations without monkey patching or wrapping numpy.
 
 It has a complete test coverage. It runs in Python 2.6+ and 3.2+ with no other dependency. It licensed under BSD.
 
 
=== modified file 'docs/nonmult.rst'
--- docs/nonmult.rst	2014-09-05 23:26:05 +0000
+++ docs/nonmult.rst	2015-01-07 15:51:38 +0000
@@ -4,17 +4,17 @@
 Temperature conversion
 ======================
 
-Unlike meters and seconds, fahrenheits, celsius and kelvin are not
-multiplicative units. Temperature is expressed in a system with a
-reference point, and relations between temperature units include
-not only an scaling factor but also an offset. Pint supports these
-type of units and conversions between them. The default definition
-file includes fahrenheits, celsius, kelvin and rankine abbreviated
-as degF, degC, degK, and degR.
+Unlike meters and seconds, the temperature units fahrenheits and
+celsius are non-multiplicative units. These temperature units are 
+expressed in a system with a reference point, and relations between
+temperature units include not only a scaling factor but also an offset.
+Pint supports these type of units and conversions between them. 
+The default definition file includes fahrenheits, celsius,
+kelvin and rankine abbreviated as degF, degC, degK, and degR.
 
 For example, to convert from celsius to fahrenheit:
 
-.. testsetup:: *
+.. testsetup::
 
    from pint import UnitRegistry
    ureg = UnitRegistry()
@@ -24,21 +24,23 @@
 
    >>> from pint import UnitRegistry
    >>> ureg = UnitRegistry()
-   >>> home = 25.4 * ureg.degC
+   >>> Q_ = ureg.Quantity
+   >>> home = Q_(25.4, ureg.degC)
    >>> print(home.to('degF'))
-   77.72000039999993 degF
+   77.7200004 degF
 
 or to other kelvin or rankine:
 
 .. doctest::
 
-    >>> print(home.to('degK'))
-    298.54999999999995 degK
+    >>> print(home.to('kelvin'))
+    298.55 kelvin
     >>> print(home.to('degR'))
     537.39 degR
 
-Additionally, for every temperature unit in the registry,
-there is also a *delta* counterpart to specify differences.
+Additionally, for every non-multiplicative temperature unit
+in the registry, there is also a *delta* counterpart to specify 
+differences. Absolute units have no *delta* counterpart.
 For example, the change in celsius is equal to the change
 in kelvin, but not in fahrenheit (as the scaling factor
 is different).
@@ -46,20 +48,61 @@
 .. doctest::
 
    >>> increase = 12.3 * ureg.delta_degC
-   >>> print(increase.to(ureg.delta_degK))
-   12.3 delta_degK
+   >>> print(increase.to(ureg.kelvin))
+   12.3 kelvin
    >>> print(increase.to(ureg.delta_degF))
-   6.833333333333334 delta_degF
+   22.14 delta_degF
 
 ..
-    Subtraction of two temperatures also yields a *delta* unit.
-
-    .. doctest::
-
-        >>> 25.4 * ureg.degC - 10. * ureg.degC
-        15.4 delta_degC
-
-Differences in temperature are multiplicative:
+Subtraction of two temperatures given in offset units yields a *delta* unit:
+
+.. doctest::
+
+    >>> Q_(25.4, ureg.degC) - Q_(10., ureg.degC)
+    <Quantity(15.4, 'delta_degC')>
+
+You can add or subtract a quantity with *delta* unit and a quantity with 
+offset unit:
+
+.. doctest::
+
+    >>> Q_(25.4, ureg.degC) + Q_(10., ureg.delta_degC)
+    <Quantity(35.4, 'degC')>
+    >>> Q_(25.4, ureg.degC) - Q_(10., ureg.delta_degC)
+    <Quantity(15.4, 'degC')>
+
+If you want to add a quantity with absolute unit to one with offset unit, like here
+
+.. doctest::
+
+    >>> heating_rate = 0.5 * ureg.kelvin/ureg.min
+    >>> Q_(10., ureg.degC) + heating_rate * Q_(30, ureg.min)
+    Traceback (most recent call last):
+            ...
+    pint.unit.OffsetUnitCalculusError: Ambiguous operation with offset unit (degC, kelvin).
+
+you have to avoid the ambiguity by either converting the offset unit to the 
+absolute unit before addition
+
+.. doctest::
+
+    >>> Q_(10., ureg.degC).to(ureg.kelvin) + heating_rate * Q_(30, ureg.min)
+    <Quantity(298.15, 'kelvin')>
+
+or convert the absolute unit to a *delta* unit:
+
+.. doctest::
+
+    >>> Q_(10., ureg.degC) + heating_rate.to('delta_degC/min') * Q_(30, ureg.min)
+    <Quantity(25.0, 'degC')>
+
+In contrast to subtraction, the addition of quantities with offset units 
+is ambiguous, e.g. for *10 degC + 100 degC* two different result are reasonable
+depending on the context, *110 degC* or *383.15 °C (= 283.15 K + 373.15 K)*.
+Because of this ambiguity pint raises an error for the addition of two 
+quantities with offset units (since pint-0.6).
+
+Quantities with *delta* units are multiplicative:
 
 .. doctest::
 
@@ -67,7 +110,55 @@
     >>> print(speed.to('delta_degC/second'))
     1.0 delta_degC / second
 
-The parser knows about *delta* units and use them when a temperature unit
+However, multiplication, division and exponentiation of quantities with 
+offset units is problematic just like addition. Pint (since version 0.6)
+will by default raise an error when a quantity with offset unit is used in
+these operations. Due to this quantities with offset units cannot be created
+like other quantities by multiplication of magnitude and unit but have
+to be explicitly created:
+
+.. doctest::
+
+    >>> home = 25.4 * ureg.degC
+    Traceback (most recent call last):
+        ...
+    pint.unit.OffsetUnitCalculusError: Ambiguous operation with offset unit (degC).
+    >>> Q_(25.4, ureg.degC)
+    <Quantity(25.4, 'degC')>
+
+As an alternative to raising an error, pint can be configured to work more
+relaxed via setting the UnitRegistry parameter *autoconvert_offset_to_baseunit*
+to true. In this mode, pint behaves differently:
+
+* Multiplication of a quantity with a single offset unit with order +1 by
+  a number or ndarray yields the quantity in the given unit.
+
+.. doctest::
+
+    >>> ureg = UnitRegistry(autoconvert_offset_to_baseunit = True)
+    >>> T = 25.4 * ureg.degC
+    >>> T
+    <Quantity(25.4, 'degC')>
+    
+* Before all other multiplications, all divisions and in case of 
+  exponentiation [#f1]_ involving quantities with offset-units, pint 
+  will convert the quantities with offset units automatically to the 
+  corresponding base unit before performing the operation. 
+
+    >>> 1/T
+    <Quantity(0.00334952269302, '1 / kelvin')>
+    >>> T * 10 * ureg.meter
+    <Quantity(527.15, 'kelvin * meter')>
+
+You can change the behaviour at any time:
+
+    >>> ureg.autoconvert_offset_to_baseunit = False
+    >>> 1/T
+    Traceback (most recent call last):
+        ...
+    pint.unit.OffsetUnitCalculusError: Ambiguous operation with offset unit (degC).
+
+The parser knows about *delta* units and uses them when a temperature unit
 is found in a multiplicative context. For example, here:
 
 .. doctest::
@@ -86,9 +177,15 @@
 
 .. doctest::
 
-    >>> print(ureg.parse_units('degC/meter', to_delta=False))
+    >>> print(ureg.parse_units('degC/meter', as_delta=False))
     degC / meter
 
+Note that the magnitude is left unchanged:
+
+.. doctest::
+
+    >>> Q_(10, 'degC/meter')
+    <Quantity(10, 'delta_degC / meter')>
 
 To define a new temperature, you need to specify the offset. For example,
 this is the definition of the celsius and fahrenheit::
@@ -98,3 +195,5 @@
 
 You do not need to define *delta* units, as they are defined automatically.
 
+.. [#f1] If the exponent is +1, the quantity will not be converted to base
+         unit but remains unchanged.
 \ No newline at end of file
 
=== modified file 'docs/serialization.rst'
--- docs/serialization.rst	2014-09-05 23:26:05 +0000
+++ docs/serialization.rst	2015-01-07 15:51:38 +0000
@@ -19,7 +19,7 @@
    >>> import pint
    >>> ureg = pint.UnitRegistry()
    >>> duration = 24.2 * ureg.years
-   >>> print(duration)
+   >>> duration
    <Quantity(24.2, 'year')>
    >>> serialized = str(duration)
    >>> print(serialized)
@@ -37,7 +37,7 @@
    >>> ureg = pint.UnitRegistry()
    >>> duration = ureg('24.2 year')
    >>> print(duration)
-   <Quantity(24.2, 'year')>
+   24.2 year
 
 Notice that the serialized quantity is likely to be parsed in **another** registry
 as shown in this example. Pint Quantities do not exist on their own but they are
@@ -72,6 +72,7 @@
 
     >>> magnitude, units = pickle.loads(serialized)
     >>> ureg.Quantity(magnitude, units)
+    <Quantity(24.2, 'year')>
 
 You can use the same mechanism with any serialization protocol, not only with binary ones.
 (In fact, version 0 of the Pickle protocol is ascii). Other common serialization protocols/packages
 
=== modified file 'docs/tutorial.rst'
--- docs/tutorial.rst	2014-09-05 23:26:05 +0000
+++ docs/tutorial.rst	2015-01-07 15:51:38 +0000
@@ -96,7 +96,6 @@
    >>> print(height)
    5.75 foot
    >>> height.ito_base_units()
-   <Quantity(1.7526, 'meter')>
    >>> print(height)
    1.7526 meter
 
 
=== modified file 'pint/__init__.py'
--- pint/__init__.py	2014-09-05 23:26:05 +0000
+++ pint/__init__.py	2015-01-07 15:51:38 +0000
@@ -16,25 +16,19 @@
 import subprocess
 import pkg_resources
 from .formatting import formatter
-from .unit import UnitRegistry, DimensionalityError, UndefinedUnitError, LazyRegistry
+from .unit import (UnitRegistry, DimensionalityError, OffsetUnitCalculusError,
+                   UndefinedUnitError, LazyRegistry)
 from .util import pi_theorem, logger
 
 from .context import Context
 
 
-__version__ = "unknown"
-try:                    # pragma: no cover
-    # try to grab the commit version of our package
-    __version__ = (subprocess.check_output(["git", "describe"],
-                                           stderr=subprocess.STDOUT,
-                                           cwd=os.path.dirname(os.path.abspath(__file__)))).strip()
-except:                 # pragma: no cover
-    # on any error just try to grab the version that is installed on the system
-    try:
-        __version__ = pkg_resources.get_distribution('pint').version
-    except:             # pragma: no cover
-        pass  # we seem to have a local copy without any repository control or installed without setuptools
-              # so the reported version will be __unknown__
+try:                # pragma: no cover
+    __version__ = pkg_resources.get_distribution('pint').version
+except:             # pragma: no cover
+    # we seem to have a local copy not installed without setuptools
+    # so the reported version will be unknown
+    __version__ = "unknown"
 
 
 #: A Registry with the default units and constants.
@@ -81,6 +75,47 @@
             sys.exit(1)
 
 
+def _check_travis(data):   # pragma: no cover
+    """Check if Travis reports that everything is ok.
+    (used to perform checks before releasing a new version).
+    """
+    import json
+    import sys
+
+    from zest.releaser.utils import system, ask
+    if not ask('Check with Travis before releasing?'):
+        return
+
+    try:
+        # Python 3
+        from urllib.request import urlopen
+        def get(url):
+            return urlopen(url).read().decode('utf-8')
+
+    except ImportError:
+        # Python 2
+        from urllib2 import urlopen
+        def get(url):
+            return urlopen(url).read()
+
+    url = 'https://api.github.com/repos/%s/%s/status/%s'
+
+    username = 'hgrecco'
+    repo = 'pint'
+    commit = system('git rev-parse HEAD')
+
+    try:
+        result = json.loads(get(url % (username, repo, commit)))['state']
+        print('Travis says: %s' % result)
+        if result != 'success':
+            if not ask('Do you want to continue anyway?', default=False):
+                sys.exit(1)
+    except Exception:
+        print('Could not determine the commit state with Travis.')
+        if ask('Do you want to continue anyway?', default=False):
+            sys.exit(1)
+
+
 def test():
     """Run all tests.
 
 
=== modified file 'pint/default_en.txt'
--- pint/default_en.txt	2014-09-05 23:26:05 +0000
+++ pint/default_en.txt	2015-01-07 15:51:38 +0000
@@ -10,7 +10,7 @@
 femto- = 1e-15 = f-
 pico- =  1e-12 = p-
 nano- =  1e-9  = n-
-micro- = 1e-6  = u-
+micro- = 1e-6  = u- = µ-
 milli- = 1e-3  = m-
 centi- = 1e-2  = c-
 deci- =  1e-1  = d-
@@ -76,7 +76,7 @@
 coulomb = ampere * second = C
 volt = joule / coulomb = V
 farad = coulomb / volt = F
-ohm = volt / ampere
+ohm = volt / ampere = Ω
 siemens = ampere / volt = S = mho
 weber = volt * second = Wb
 tesla = weber / meter ** 2 = T
@@ -138,7 +138,7 @@
 baud = bit / second = Bd = bps
 
 # Length
-angstrom = 1e-10 * meter
+angstrom = 1e-10 * meter = ångström = Å
 inch = 2.54 * centimeter = in = international_inch = inches = international_inches 
 foot = 12 * inch = ft = international_foot = feet = international_feet
 mile = 5280 * foot = mi = international_mile
@@ -291,7 +291,7 @@
 pint = quart / 2 = pt = liquid_pint = US_liquid_pint
 cup = pint / 2 = liquid_cup = US_liquid_cup
 gill = cup / 2 = liquid_gill = US_liquid_gill
-floz = gill / 4 = fluid_ounce = US_fluid_ounce = US_liquid_ounce
+fluid_ounce = gill / 4 = floz = US_fluid_ounce = US_liquid_ounce
 imperial_bushel = 36.36872 * liter = UK_bushel
 imperial_gallon = imperial_bushel / 8 = UK_gallon
 imperial_quart = imperial_gallon / 4 = UK_quart
@@ -318,3 +318,33 @@
     [temperature] -> [energy]: boltzmann_constant * value
     [energy] -> [temperature]: value / boltzmann_constant
 @end
+
+@context(mw=0,volume=0,solvent_mass=0) chemistry = chem
+    # mw is the molecular weight of the species
+    # volume is the volume of the solution
+    # solvent_mass is the mass of solvent in the solution
+    
+    # moles -> mass require the molecular weight
+    [substance] -> [mass]: value * mw
+    [mass] -> [substance]: value / mw
+
+    # moles/volume -> mass/volume and moles/mass -> mass / mass 
+    # require the  molecular weight
+    [substance] / [volume] -> [mass] / [volume]: value * mw
+    [mass] / [volume] -> [substance] / [volume]: value / mw
+    [substance] / [mass] -> [mass] / [mass]: value * mw
+    [mass] / [mass] -> [substance] / [mass]: value / mw
+
+    # moles/volume -> moles requires the solution volume
+    [substance] / [volume] -> [substance]: value * volume
+    [substance] -> [substance] / [volume]: value / volume
+
+    # moles/mass -> moles requires the solvent (usually water) mass
+    [substance] / [mass] -> [substance]: value * solvent_mass
+    [substance] -> [substance] / [mass]: value / solvent_mass
+
+    # moles/mass -> moles/volume require the solvent mass and the volume
+    [substance] / [mass] -> [substance]/[volume]: value * solvent_mass / volume
+    [substance] / [volume] -> [substance] / [mass]: value / solvent_mass * volume
+
+@end
 
=== modified file 'pint/quantity.py'
--- pint/quantity.py	2014-09-05 23:26:05 +0000
+++ pint/quantity.py	2015-01-07 15:51:38 +0000
@@ -15,7 +15,8 @@
 import functools
 
 from .formatting import remove_custom_flags
-from .unit import DimensionalityError, UnitsContainer, UnitDefinition, UndefinedUnitError
+from .unit import (DimensionalityError, OffsetUnitCalculusError,
+                   UnitsContainer, UnitDefinition, UndefinedUnitError)
 from .compat import string_types, ndarray, np, _to_magnitude, long_type
 from .util import logger
 
@@ -48,6 +49,8 @@
         # Both quantities are the same class and therefore from the same registry.
         # (Each registry has its own Quantity class)
         return True
+    elif q1._REGISTRY is getattr(other, '_REGISTRY', None):
+        return True
     elif isinstance(other, _Quantity):
         # The other object is a Quantity but from another registry.
         raise ValueError('Cannot operate between quantities of different registries')
@@ -55,21 +58,8 @@
     return False
 
 
-def _only_multiplicative_units(q):
-    """Check if the quantity has non-multiplicative units.
-    """
-
-    # Compound units are never multiplicative
-    if len(q.units) != 1:
-        return True
-
-    unit = list(q.units.keys())[0]
-
-    return q._REGISTRY._units[unit].is_multiplicative
-
-
 class _Quantity(object):
-    """Implements a class to describe a physical quantities:
+    """Implements a class to describe a physical quantity:
     the product of a numerical value and a unit of measurement.
 
     :param value: value of the physical quantity to be created.
@@ -138,7 +128,7 @@
         spec = spec or self.default_format
 
         if '~' in spec:
-            units = UnitsContainer(dict((self._REGISTRY.get_symbol(key), value)
+            units = UnitsContainer(dict((self._REGISTRY._get_symbol(key), value)
                                    for key, value in self.units.items()))
             spec = spec.replace('~', '')
         else:
@@ -304,15 +294,8 @@
         :param op: operator function (e.g. operator.add, operator.isub)
         :type op: function
         """
-        if _check(self, other):
-            if not self.dimensionality == other.dimensionality:
-                raise DimensionalityError(self.units, other.units,
-                                          self.dimensionality, other.dimensionality)
-            if self._units == other._units:
-                self._magnitude = op(self._magnitude, other._magnitude)
-            else:
-                self._magnitude = op(self._magnitude, other.to(self)._magnitude)
-        else:
+        if not _check(self, other):
+            # other not from same Registry or not a Quantity
             try:
                 other_magnitude = _to_magnitude(other, self.force_ndarray)
             except TypeError:
@@ -328,6 +311,75 @@
                 self._magnitude = op(self._magnitude, other_magnitude)
             else:
                 raise DimensionalityError(self.units, 'dimensionless')
+            return self
+
+        if not self.dimensionality == other.dimensionality:
+            raise DimensionalityError(self.units, other.units,
+                                      self.dimensionality,
+                                      other.dimensionality)
+
+        # Next we define some variables to make if-clauses more readable.
+        self_non_mul_units = self._get_non_multiplicative_units()
+        is_self_multiplicative = len(self_non_mul_units) == 0
+        if len(self_non_mul_units) == 1:
+            self_non_mul_unit = self_non_mul_units[0]
+        other_non_mul_units = other._get_non_multiplicative_units()
+        is_other_multiplicative = len(other_non_mul_units) == 0
+        if len(other_non_mul_units) == 1:
+            other_non_mul_unit = other_non_mul_units[0]
+
+        # Presence of non-multiplicative units gives rise to several cases.
+        if is_self_multiplicative and is_other_multiplicative:
+            if self._units == other._units:
+                self._magnitude = op(self._magnitude, other._magnitude)
+            # If only self has a delta unit, other determines unit of result.
+            elif self._get_delta_units() and not other._get_delta_units():
+                self._magnitude = op(self._convert_magnitude(other.units),
+                                     other._magnitude)
+                self._units = copy.copy(other.units)
+            else:
+                self._magnitude = op(self._magnitude,
+                                     other.to(self.units)._magnitude)
+
+        elif (op == operator.isub and len(self_non_mul_units) == 1
+                and self.units[self_non_mul_unit] == 1
+                and not other._has_compatible_delta(self_non_mul_unit)):
+            if self.units == other.units:
+                self._magnitude = op(self._magnitude, other._magnitude)
+            else:
+                self._magnitude = op(self._magnitude,
+                                     other.to(self.units)._magnitude)
+            self.units['delta_' + self_non_mul_unit
+                       ] = self.units.pop(self_non_mul_unit)
+
+        elif (op == operator.isub and len(other_non_mul_units) == 1
+                and other.units[other_non_mul_unit] == 1
+                and not self._has_compatible_delta(other_non_mul_unit)):
+            # we convert to self directly since it is multiplicative
+            self._magnitude = op(self._magnitude,
+                                other.to(self.units)._magnitude)
+
+        elif (len(self_non_mul_units) == 1
+                # order of the dimension of offset unit == 1 ?
+                and self._units[self_non_mul_unit] == 1
+                and other._has_compatible_delta(self_non_mul_unit)):
+            tu = copy.copy(self.units)
+            # Replace offset unit in self by the corresponding delta unit.
+            # This is done to prevent a shift by offset in the to()-call.
+            tu['delta_' + self_non_mul_unit] = tu.pop(self_non_mul_unit)
+            self._magnitude = op(self._magnitude, other.to(tu)._magnitude)
+        elif (len(other_non_mul_units) == 1
+                # order of the dimension of offset unit == 1 ?
+                and other._units[other_non_mul_unit] == 1
+                and self._has_compatible_delta(other_non_mul_unit)):
+            tu = copy.copy(other.units)
+            # Replace offset unit in other by the corresponding delta unit.
+            # This is done to prevent a shift by offset in the to()-call.
+            tu['delta_' + other_non_mul_unit] = tu.pop(other_non_mul_unit)
+            self._magnitude = op(self._convert_magnitude(tu), other._magnitude)
+            self._units = copy.copy(other.units)
+        else:
+            raise OffsetUnitCalculusError(self.units, other.units)
 
         return self
 
@@ -339,17 +391,8 @@
         :param op: operator function (e.g. operator.add, operator.isub)
         :type op: function
         """
-        if _check(self, other):
-            if not self.dimensionality == other.dimensionality:
-                raise DimensionalityError(self.units, other.units,
-                                          self.dimensionality, other.dimensionality)
-            if self._units == other._units:
-                magnitude = op(self._magnitude, other._magnitude)
-            else:
-                magnitude = op(self._magnitude, other.to(self)._magnitude)
-
-            units = copy.copy(self.units)
-        else:
+        if not _check(self, other):
+            # other not from same Registry or not a Quantity
             if _eq(other, 0, True):
                 # If the other value is 0 (but not Quantity 0)
                 # do the operation without checking units.
@@ -364,6 +407,79 @@
                                _to_magnitude(other, self.force_ndarray))
             else:
                 raise DimensionalityError(self.units, 'dimensionless')
+            return self.__class__(magnitude, units)
+
+        if not self.dimensionality == other.dimensionality:
+            raise DimensionalityError(self.units, other.units,
+                                      self.dimensionality,
+                                      other.dimensionality)
+
+        # Next we define some variables to make if-clauses more readable.
+        self_non_mul_units = self._get_non_multiplicative_units()
+        is_self_multiplicative = len(self_non_mul_units) == 0
+        if len(self_non_mul_units) == 1:
+            self_non_mul_unit = self_non_mul_units[0]
+        other_non_mul_units = other._get_non_multiplicative_units()
+        is_other_multiplicative = len(other_non_mul_units) == 0
+        if len(other_non_mul_units) == 1:
+            other_non_mul_unit = other_non_mul_units[0]
+
+        # Presence of non-multiplicative units gives rise to several cases.
+        if is_self_multiplicative and is_other_multiplicative:
+            if self._units == other._units:
+                magnitude = op(self._magnitude, other._magnitude)
+                units = copy.copy(self.units)
+            # If only self has a delta unit, other determines unit of result.
+            elif self._get_delta_units() and not other._get_delta_units():
+                magnitude = op(self._convert_magnitude(other.units),
+                               other._magnitude)
+                units = copy.copy(other.units)
+            else:
+                units = copy.copy(self.units)
+                magnitude = op(self._magnitude,
+                               other.to(self.units).magnitude)
+
+        elif (op == operator.sub and len(self_non_mul_units) == 1
+                and self.units[self_non_mul_unit] == 1
+                and not other._has_compatible_delta(self_non_mul_unit)):
+            if self.units == other.units:
+                magnitude = op(self._magnitude, other._magnitude)
+            else:
+                magnitude = op(self._magnitude,
+                               other.to(self.units)._magnitude)
+            units = copy.copy(self.units)
+            units['delta_' + self_non_mul_unit] = units.pop(self_non_mul_unit)
+
+        elif (op == operator.sub and len(other_non_mul_units) == 1
+                and other.units[other_non_mul_unit] == 1
+                and not self._has_compatible_delta(other_non_mul_unit)):
+            # we convert to self directly since it is multiplicative
+            magnitude = op(self._magnitude,
+                           other.to(self.units)._magnitude)
+            units = copy.copy(self.units)
+
+        elif (len(self_non_mul_units) == 1
+                # order of the dimension of offset unit == 1 ?
+                and self._units[self_non_mul_unit] == 1
+                and other._has_compatible_delta(self_non_mul_unit)):
+            tu = copy.copy(self.units)
+            # Replace offset unit in self by the corresponding delta unit.
+            # This is done to prevent a shift by offset in the to()-call.
+            tu['delta_' + self_non_mul_unit] = tu.pop(self_non_mul_unit)
+            magnitude = op(self._magnitude, other.to(tu).magnitude)
+            units = copy.copy(self.units)
+        elif (len(other_non_mul_units) == 1
+                # order of the dimension of offset unit == 1 ?
+                and other._units[other_non_mul_unit] == 1
+                and self._has_compatible_delta(other_non_mul_unit)):
+            tu = copy.copy(other.units)
+            # Replace offset unit in other by the corresponding delta unit.
+            # This is done to prevent a shift by offset in the to()-call.
+            tu['delta_' + other_non_mul_unit] = tu.pop(other_non_mul_unit)
+            magnitude = op(self._convert_magnitude(tu), other._magnitude)
+            units = copy.copy(other.units)
+        else:
+            raise OffsetUnitCalculusError(self.units, other.units)
 
         return self.__class__(magnitude, units)
 
@@ -403,24 +519,40 @@
         if units_op is None:
             units_op = magnitude_op
 
-        if self.__used:
-            if not _only_multiplicative_units(self):
-                self.ito_base_units()
-        else:
-            self.__used = True
+        offset_units_self = self._get_non_multiplicative_units()
+        no_offset_units_self = len(offset_units_self)
 
-        if _check(self, other):
-            if not _only_multiplicative_units(other):
-                other = other.to_base_units()
-            self._magnitude = magnitude_op(self._magnitude, other._magnitude)
-            self._units = units_op(self._units, other._units)
-        else:
+        if not _check(self, other):
+            if not self._ok_for_muldiv(no_offset_units_self):
+                raise OffsetUnitCalculusError(self.units,
+                                              getattr(other, 'units', ''))
+            if len(offset_units_self) == 1:
+                if (self.units[offset_units_self[0]] != 1
+                        or magnitude_op not in [operator.mul, operator.imul]):
+                    raise OffsetUnitCalculusError(self.units,
+                                                  getattr(other, 'units', ''))
             try:
                 other_magnitude = _to_magnitude(other, self.force_ndarray)
             except TypeError:
                 return NotImplemented
             self._magnitude = magnitude_op(self._magnitude, other_magnitude)
             self._units = units_op(self._units, UnitsContainer())
+            return self
+
+        if not self._ok_for_muldiv(no_offset_units_self):
+            raise OffsetUnitCalculusError(self.units, other.units)
+        elif no_offset_units_self == 1 and len(self.units) == 1:
+                self.ito_base_units()
+
+        no_offset_units_other = len(other._get_non_multiplicative_units())
+
+        if not other._ok_for_muldiv(no_offset_units_other):
+            raise OffsetUnitCalculusError(self.units, other.units)
+        elif no_offset_units_other == 1 and len(other.units) == 1:
+            other.ito_base_units()
+
+        self._magnitude = magnitude_op(self._magnitude, other._magnitude)
+        self._units = units_op(self._units, other._units)
 
         return self
 
@@ -437,27 +569,46 @@
         if units_op is None:
             units_op = magnitude_op
 
+        offset_units_self = self._get_non_multiplicative_units()
+        no_offset_units_self = len(offset_units_self)
+
+        if not _check(self, other):
+            if not self._ok_for_muldiv(no_offset_units_self):
+                raise OffsetUnitCalculusError(self.units,
+                                              getattr(other, 'units', ''))
+            if len(offset_units_self) == 1:
+                if (self.units[offset_units_self[0]] != 1
+                        or magnitude_op not in [operator.mul, operator.imul]):
+                    raise OffsetUnitCalculusError(self.units,
+                                                  getattr(other, 'units', ''))
+            try:
+                other_magnitude = _to_magnitude(other, self.force_ndarray)
+            except TypeError:
+                return NotImplemented
+
+            magnitude = magnitude_op(self._magnitude, other_magnitude)
+            units = units_op(self._units, UnitsContainer())
+
+            return self.__class__(magnitude, units)
+
         new_self = self
-        if self.__used:
-            if not _only_multiplicative_units(self):
-                new_self = self.to_base_units()
-
-        if _check(self, other):
-            if not _only_multiplicative_units(other):
-                other = other.to_base_units()
-            magnitude = magnitude_op(new_self._magnitude, other._magnitude)
-            units = units_op(new_self._units, other._units)
-        else:
-            try:
-                other_magnitude = _to_magnitude(other, self.force_ndarray)
-            except TypeError:
-                return NotImplemented
-            magnitude = magnitude_op(new_self._magnitude, other_magnitude)
-            units = units_op(new_self._units, UnitsContainer())
-
-        ret = self.__class__(magnitude, units)
-        ret.__used = True
-        return ret
+
+        if not self._ok_for_muldiv(no_offset_units_self):
+            raise OffsetUnitCalculusError(self.units, other.units)
+        elif no_offset_units_self == 1 and len(self.units) == 1:
+            new_self = self.to_base_units()
+
+        no_offset_units_other = len(other._get_non_multiplicative_units())
+
+        if not other._ok_for_muldiv(no_offset_units_other):
+            raise OffsetUnitCalculusError(self.units, other.units)
+        elif no_offset_units_other == 1 and len(other.units) == 1:
+            other = other.to_base_units()
+
+        magnitude = magnitude_op(new_self._magnitude, other._magnitude)
+        units = units_op(new_self._units, other._units)
+
+        return self.__class__(magnitude, units)
 
     def __imul__(self, other):
         if not isinstance(self._magnitude, ndarray):
@@ -493,6 +644,13 @@
             other_magnitude = _to_magnitude(other, self.force_ndarray)
         except TypeError:
             return NotImplemented
+
+        no_offset_units_self = len(self._get_non_multiplicative_units())
+        if not self._ok_for_muldiv(no_offset_units_self):
+            raise OffsetUnitCalculusError(self.units, '')
+        elif no_offset_units_self == 1 and len(self.units) == 1:
+            self = self.to_base_units()
+
         return self.__class__(other_magnitude / self._magnitude, 1 / self._units)
 
     def __rfloordiv__(self, other):
@@ -500,6 +658,13 @@
             other_magnitude = _to_magnitude(other, self.force_ndarray)
         except TypeError:
             return NotImplemented
+
+        no_offset_units_self = len(self._get_non_multiplicative_units())
+        if not self._ok_for_muldiv(no_offset_units_self):
+            raise OffsetUnitCalculusError(self.units, '')
+        elif no_offset_units_self == 1 and len(self.units) == 1:
+            self = self.to_base_units()
+
         return self.__class__(other_magnitude // self._magnitude, 1 / self._units)
 
     __div__ = __truediv__
@@ -515,10 +680,36 @@
         except TypeError:
             return NotImplemented
         else:
-            if not _only_multiplicative_units(self):
-                self.ito_base_units()
+            if not self._ok_for_muldiv:
+                raise OffsetUnitCalculusError(self.units)
+
+            if isinstance(getattr(other, '_magnitude', other), ndarray):
+                # arrays are refused as exponent, because they would create
+                #  len(array) quanitites of len(set(array)) different units
+                if np.size(other) > 1:
+                    raise DimensionalityError(self.units, 'dimensionless')
+
+            new_self = self
+            if other == 1:
+                return self
+            elif other == 0:
+                self._units = UnitsContainer()
+            else:
+                if not self._is_multiplicative:
+                    if self._REGISTRY.autoconvert_offset_to_baseunit:
+                        self.ito_base_units()
+                    else:
+                        raise OffsetUnitCalculusError(self.units)
+
+                if getattr(other, 'dimensionless', False):
+                    other = other.to_base_units()
+                    self._units **= other.magnitude
+                elif not getattr(other, 'dimensionless', True):
+                    raise DimensionalityError(self.units, 'dimensionless')
+                else:
+                    self._units **= other
+
             self._magnitude **= _to_magnitude(other, self.force_ndarray)
-            self._units **= other
             return self
 
     def __pow__(self, other):
@@ -527,14 +718,51 @@
         except TypeError:
             return NotImplemented
         else:
+            if not self._ok_for_muldiv:
+                raise OffsetUnitCalculusError(self.units)
+
+            if isinstance(getattr(other, '_magnitude', other), ndarray):
+                # arrays are refused as exponent, because they would create
+                #  len(array) quantities of len(set(array)) different units
+                if np.size(other) > 1:
+                    raise DimensionalityError(self.units, 'dimensionless')
+
             new_self = self
-            if not _only_multiplicative_units(self):
-                new_self = self.to_base_units()
+            if other == 1:
+                return self
+            elif other == 0:
+                units = UnitsContainer()
+            else:
+                if not self._is_multiplicative:
+                    if self._REGISTRY.autoconvert_offset_to_baseunit:
+                        new_self = self.to_base_units()
+                    else:
+                        raise OffsetUnitCalculusError(self.units)
+
+                if getattr(other, 'dimensionless', False):
+                    units = new_self._units ** other.to_base_units().magnitude
+                elif not getattr(other, 'dimensionless', True):
+                    raise DimensionalityError(self.units, 'dimensionless')
+                else:
+                    units = new_self._units ** other
 
             magnitude = new_self._magnitude ** _to_magnitude(other, self.force_ndarray)
-            units = new_self._units ** other
             return self.__class__(magnitude, units)
 
+    def __rpow__(self, other):
+        try:
+            other_magnitude = _to_magnitude(other, self.force_ndarray)
+        except TypeError:
+            return NotImplemented
+        else:
+            if not self.dimensionless:
+                raise DimensionalityError(self.units, 'dimensionless')
+            if isinstance(self._magnitude, ndarray):
+                if np.size(self._magnitude) > 1:
+                    raise DimensionalityError(self.units, 'dimensionless')
+            new_self = self.to_base_units()
+            return other**new_self._magnitude
+
     def __abs__(self):
         return self.__class__(abs(self._magnitude), self._units)
 
@@ -798,7 +1026,10 @@
 
             if isinstance(factor, self.__class__):
                 if not factor.dimensionless:
-                    raise ValueError
+                    raise DimensionalityError(value, self.units,
+                                              extra_msg='. Assign a quantity with the same dimensionality or '
+                                                        'access the magnitude directly as '
+                                                        '`obj.magnitude[%s] = %s`' % (key, value))
                 self._magnitude[key] = factor.magnitude
             else:
                 self._magnitude[key] = factor
@@ -961,3 +1192,58 @@
                 error = error * abs(self.magnitude)
 
         return self._REGISTRY.Measurement(copy.copy(self.magnitude), error, self.units)
+
+    # methods/properties that help for math operations with offset units
+    @property
+    def _is_multiplicative(self):
+        """Check if the Quantity object has only multiplicative units.
+        """
+        # XXX Turn this into a method/property of _Quantity?
+        return not self._get_non_multiplicative_units()
+
+    def _get_non_multiplicative_units(self):
+        """Return a list of the of non-multiplicative units of the Quantity object
+        """
+        offset_units = [unit for unit in self.units.keys()
+                        if not self._REGISTRY._units[unit].is_multiplicative]
+        return offset_units
+
+    def _get_delta_units(self):
+        """Return list of delta units ot the Quantity object
+        """
+        delta_units = [u for u in self.units.keys() if u.startswith("delta_")]
+        return delta_units
+
+    def _has_compatible_delta(self, unit):
+        """"Check if Quantity object has a delta_unit that is compatible with unit
+        """
+        deltas = self._get_delta_units()
+        if 'delta_' + unit in deltas:
+            return True
+        else:  # Look for delta units with same dimension as the offset unit
+            offset_unit_dim = self._REGISTRY._units[unit].reference
+            for d in deltas:
+                if self._REGISTRY._units[d].reference == offset_unit_dim:
+                    return True
+        return False
+
+    def _ok_for_muldiv(self, no_offset_units=None):
+        """Checks if Quantity object can be multiplied or divided
+
+        :q: quantity object that is checked
+        :no_offset_units: number of offset units in q
+        """
+        is_ok = True
+        if no_offset_units is None:
+            no_offset_units = len(self._get_non_multiplicative_units())
+        if no_offset_units > 1:
+            is_ok = False
+        if no_offset_units == 1:
+            if len(self._units) > 1:
+                is_ok = False
+            if (len(self._units) == 1
+                    and not self._REGISTRY.autoconvert_offset_to_baseunit):
+                is_ok = False
+            if next(iter(self._units.values())) != 1:
+                is_ok = False
+        return is_ok
 
=== added file 'pint/testsuite/parameterized.py'
--- pint/testsuite/parameterized.py	1970-01-01 00:00:00 +0000
+++ pint/testsuite/parameterized.py	2015-01-07 15:51:38 +0000
@@ -0,0 +1,152 @@
+# -*- coding: utf-8 -*-
+#
+# Adds Parameterized tests for Python's unittest module
+#
+# Code from: parameterizedtestcase, version: 0.1.0
+# Homepage: https://github.com/msabramo/python_unittest_parameterized_test_case
+# Author: Marc Abramowitz, email: [e-mail]
+# License: MIT
+#
+# Fixed for to work in Python 2 & 3 with "add_metaclass" decorator from six
+# https://pypi.python.org/pypi/six
+# Author: Benjamin Peterson
+# License: MIT 
+#
+# Use like this:
+#
+#    from parameterizedtestcase import ParameterizedTestCase
+#
+#    class MyTests(ParameterizedTestCase):
+#        @ParameterizedTestCase.parameterize(
+#            ("input", "expected_output"),
+#            [
+#                ("2+4", 6),
+#                ("3+5", 8),
+#                ("6*9", 54),
+#            ]
+#        )
+#        def test_eval(self, input, expected_output):
+#            self.assertEqual(eval(input), expected_output)
+
+try:
+    import unittest2 as unittest
+except ImportError:  # pragma: no cover
+    import unittest
+
+from functools import wraps
+import collections
+
+
+def add_metaclass(metaclass):
+    """Class decorator for creating a class with a metaclass."""
+    def wrapper(cls):
+        orig_vars = cls.__dict__.copy()
+        orig_vars.pop('__dict__', None)
+        orig_vars.pop('__weakref__', None)
+        slots = orig_vars.get('__slots__')
+        if slots is not None:
+            if isinstance(slots, str):
+                slots = [slots]
+            for slots_var in slots:
+                orig_vars.pop(slots_var)
+        return metaclass(cls.__name__, cls.__bases__, orig_vars)
+    return wrapper
+
+
+def augment_method_docstring(method, new_class_dict, classname,
+                             param_names, param_values, new_method):
+    param_assignments_str = '; '.join(
+        ['%s = %s' % (k, v) for (k, v) in zip(param_names, param_values)])
+    extra_doc = "%s (%s.%s) [with %s] " % (
+        method.__name__, new_class_dict.get('__module__', '<module>'),
+        classname, param_assignments_str)
+
+    try:
+        new_method.__doc__ = extra_doc + new_method.__doc__
+    except TypeError:  # Catches when new_method.__doc__ is None
+        new_method.__doc__ = extra_doc
+
+
+class ParameterizedTestCaseMetaClass(type):
+    method_counter = {}
+
+    def __new__(meta, classname, bases, class_dict):
+        new_class_dict = {}
+
+        for attr_name, attr_value in list(class_dict.items()):
+            if isinstance(attr_value, collections.Callable) and hasattr(attr_value, 'param_names'):
+                # print("Processing attr_name = %r; attr_value = %r" % (
+                #     attr_name, attr_value))
+
+                method = attr_value
+                param_names = attr_value.param_names
+                data = attr_value.data
+                func_name_format = attr_value.func_name_format
+
+                meta.process_method(
+                    classname, method, param_names, data, new_class_dict,
+                    func_name_format)
+            else:
+                new_class_dict[attr_name] = attr_value
+
+        return type.__new__(meta, classname, bases, new_class_dict)
+
+    @classmethod
+    def process_method(
+            cls, classname, method, param_names, data, new_class_dict,
+            func_name_format):
+        method_counter = cls.method_counter
+
+        for param_values in data:
+            new_method = cls.new_method(method, param_values)
+            method_counter[method.__name__] = \
+                method_counter.get(method.__name__, 0) + 1
+            case_data = dict(list(zip(param_names, param_values)))
+            case_data['func_name'] = method.__name__
+            case_data['case_num'] = method_counter[method.__name__]
+
+            new_method.__name__ = func_name_format.format(**case_data)
+
+            augment_method_docstring(
+                method, new_class_dict, classname,
+                param_names, param_values, new_method)
+            new_class_dict[new_method.__name__] = new_method
+
+    @classmethod
+    def new_method(cls, method, param_values):
+        @wraps(method)
+        def new_method(self):
+            return method(self, *param_values)
+
+        return new_method
+
+@add_metaclass(ParameterizedTestCaseMetaClass)
+class ParameterizedTestMixin(object):
+    @classmethod
+    def parameterize(cls, param_names, data,
+                     func_name_format='{func_name}_{case_num:05d}'):
+        """Decorator for parameterizing a test method - example:
+
+        @ParameterizedTestCase.parameterize(
+            ("isbn", "expected_title"), [
+                ("0262033844", "Introduction to Algorithms"),
+                ("0321558146", "Campbell Essential Biology")])
+
+        """
+
+        def decorator(func):
+            @wraps(func)
+            def newfunc(*arg, **kwargs):
+                return func(*arg, **kwargs)
+
+            newfunc.param_names = param_names
+            newfunc.data = data
+            newfunc.func_name_format = func_name_format
+
+            return newfunc
+
+        return decorator
+
+@add_metaclass(ParameterizedTestCaseMetaClass)
+class ParameterizedTestCase(unittest.TestCase, ParameterizedTestMixin):
+    pass
 
=== modified file 'pint/testsuite/test_issues.py'
--- pint/testsuite/test_issues.py	2014-09-05 23:26:05 +0000
+++ pint/testsuite/test_issues.py	2015-01-07 15:51:38 +0000
@@ -16,6 +16,9 @@
 
     FORCE_NDARRAY = False
 
+    def setup(self):
+        self.ureg.autoconvert_offset_to_baseunit = False
+
     @unittest.expectedFailure
     def test_issue25(self):
         x = ParserHelper.from_string('10 %')
@@ -92,9 +95,9 @@
     def test_issue66b(self):
         ureg = UnitRegistry()
         self.assertEqual(ureg.get_base_units(ureg.kelvin.units),
-                         (None, UnitsContainer({'kelvin': 1})))
+                         (1.0, UnitsContainer({'kelvin': 1})))
         self.assertEqual(ureg.get_base_units(ureg.degC.units),
-                         (None, UnitsContainer({'kelvin': 1})))
+                         (1.0, UnitsContainer({'kelvin': 1})))
 
     def test_issue69(self):
         ureg = UnitRegistry()
@@ -127,11 +130,12 @@
         self.assertQuantityAlmostEqual(va.to_base_units(), vb.to_base_units())
 
     def test_issue86(self):
+        ureg = self.ureg
+        ureg.autoconvert_offset_to_baseunit = True
+
         def parts(q):
             return q.magnitude, q.units
 
-        ureg = UnitRegistry()
-
         q1 = 10. * ureg.degC
         q2 = 10. * ureg.kelvin
 
@@ -158,7 +162,6 @@
         self.assertEqual(parts(q1 / q3), (k1m / q3m, k1u / q3u))
         self.assertEqual(parts(q3 * q1), (q3m * k1m, q3u * k1u))
         self.assertEqual(parts(q3 / q1), (q3m / k1m, q3u / k1u))
-        self.assertEqual(parts(q1 **  1), (k1m **  1, k1u **  1))
         self.assertEqual(parts(q1 ** -1), (k1m ** -1, k1u ** -1))
         self.assertEqual(parts(q1 **  2), (k1m **  2, k1u **  2))
         self.assertEqual(parts(q1 ** -2), (k1m ** -2, k1u ** -2))
@@ -177,8 +180,10 @@
         self.assertQuantityAlmostEqual(v1.to_base_units(), v2)
         self.assertQuantityAlmostEqual(v1.to_base_units(), v2.to_base_units())
 
+    @unittest.expectedFailure
     def test_issue86c(self):
         ureg = self.ureg
+        ureg.autoconvert_offset_to_baseunit = True
         T = ureg.degC
         T = 100. * T
         self.assertQuantityAlmostEqual(ureg.k*2*T, ureg.k*(2*T))
 
=== modified file 'pint/testsuite/test_numpy.py'
--- pint/testsuite/test_numpy.py	2014-09-05 23:26:05 +0000
+++ pint/testsuite/test_numpy.py	2015-01-07 15:51:38 +0000
@@ -2,8 +2,13 @@
 
 from __future__ import division, unicode_literals, print_function, absolute_import
 
+import copy
+import operator as op
+
+from pint import DimensionalityError
 from pint.compat import np, unittest
 from pint.testsuite import QuantityTestCase, helpers
+from pint.testsuite.test_umath import TestUFuncs
 
 
 @helpers.requires_numpy()
@@ -189,9 +194,11 @@
         q[0] = 1*self.ureg.m
         self.assertQuantityEqual(q, [[1,1],[3,4]]*self.ureg.m)
 
-        q[0] = (1,2)*self.ureg.m
-        self.assertQuantityEqual(q, self.q)
+        q = self.q.copy()
+        q.__setitem__(Ellipsis, 1*self.ureg.m)
+        self.assertQuantityEqual(q, [[1,1],[1,1]]*self.ureg.m)
 
+        q = self.q.copy()
         q[:] = 1*self.ureg.m
         self.assertQuantityEqual(q, [[1,1],[1,1]]*self.ureg.m)
 
@@ -239,58 +246,68 @@
         self.assertQuantityEqual(u == 1, u.magnitude == 1)
 
 
-from pint.testsuite.test_umath import TestUFuncs
[e-mail]
-class TestNumpyNotSupported(TestUFuncs):
[e-mail]_numpy()
+class TestNumpyNeedsSubclassing(TestUFuncs):
 
     FORCE_NDARRAY = True
 
+    @property
+    def q(self):
+        return [1. ,2., 3., 4.] * self.ureg.J
 
+    @unittest.expectedFailure
     def test_unwrap(self):
         """unwrap depends on diff
         """
-        self.assertEqual(np.unwrap([0,3*np.pi]*self.ureg.radians), [0,np.pi])
-        self.assertEqual(np.unwrap([0,540]*self.ureg.deg), [0,180]*self.ureg.deg)
+        self.assertQuantityEqual(np.unwrap([0,3*np.pi]*self.ureg.radians), [0,np.pi])
+        self.assertQuantityEqual(np.unwrap([0,540]*self.ureg.deg), [0,180]*self.ureg.deg)
 
+    @unittest.expectedFailure
     def test_trapz(self):
         """Units are erased by asanyarray, Quantity does not inherit from NDArray
         """
-        self.assertEqual(np.trapz(self.q, dx = 1*self.ureg.m), 7.5 * self.ureg.J*self.ureg.m)
+        self.assertQuantityEqual(np.trapz(self.q, dx=1*self.ureg.m), 7.5 * self.ureg.J*self.ureg.m)
 
+    @unittest.expectedFailure
     def test_diff(self):
         """Units are erased by asanyarray, Quantity does not inherit from NDArray
         """
         self.assertQuantityEqual(np.diff(self.q, 1), [1, 1, 1] * self.ureg.J)
 
+    @unittest.expectedFailure
     def test_ediff1d(self):
         """Units are erased by asanyarray, Quantity does not inherit from NDArray
         """
-        self.assertEqual(np.ediff1d(self.q, 1), [1, 1, 1] * self.ureg.J)
+        self.assertQuantityEqual(np.ediff1d(self.q, 1 * self.ureg.J), [1, 1, 1] * self.ureg.J)
 
+    @unittest.expectedFailure
     def test_fix(self):
         """Units are erased by asanyarray, Quantity does not inherit from NDArray
         """
-        self.assertEqual(np.fix(3.14 * self.ureg.m), 3.0 * self.ureg.m)
-        self.assertEqual(np.fix(3.0 * self.ureg.m), 3.0 * self.ureg.m)
+        self.assertQuantityEqual(np.fix(3.14 * self.ureg.m), 3.0 * self.ureg.m)
+        self.assertQuantityEqual(np.fix(3.0 * self.ureg.m), 3.0 * self.ureg.m)
         self.assertQuantityEqual(
             np.fix([2.1, 2.9, -2.1, -2.9] * self.ureg.m),
             [2., 2., -2., -2.] * self.ureg.m
         )
 
+    @unittest.expectedFailure
     def test_gradient(self):
         """shape is a property not a function
         """
         l = np.gradient([[1,1],[3,4]] * self.ureg.J, 1 * self.ureg.m)
-        self.assertEqual(l[0], [[2., 3.], [2., 3.]] * self.ureg.J / self.ureg.m)
-        self.assertEqual(l[1], [[0., 0.], [1., 1.]] * self.ureg.J / self.ureg.m)
+        self.assertQuantityEqual(l[0], [[2., 3.], [2., 3.]] * self.ureg.J / self.ureg.m)
+        self.assertQuantityEqual(l[1], [[0., 0.], [1., 1.]] * self.ureg.J / self.ureg.m)
 
+    @unittest.expectedFailure
     def test_cross(self):
         """Units are erased by asarray, Quantity does not inherit from NDArray
         """
-        a = [3,-3, 1] * self.ureg.kPa
-        b = [4, 9, 2] * self.ureg.m**2
-        self.assertQuantityEqual(np.cross(a,b), [-15,-2,39]*self.ureg.kPa*self.ureg.m**2)
+        a = [[3,-3, 1]] * self.ureg.kPa
+        b = [[4, 9, 2]] * self.ureg.m**2
+        self.assertQuantityEqual(np.cross(a, b), [-15, -2, 39] * self.ureg.kPa * self.ureg.m**2)
 
+    @unittest.expectedFailure
     def test_power(self):
         """This is not supported as different elements might end up with different units
 
@@ -302,6 +319,7 @@
                     (self.qless, np.asarray([1., 2, 3, 4])),
                     (self.q2, ),)
 
+    @unittest.expectedFailure
     def test_ones_like(self):
         """Units are erased by emptyarra, Quantity does not inherit from NDArray
         """
@@ -385,3 +403,39 @@
                     (self.qless, 2),
                     (self.q1, self.q2, self.qs, ),
                     'same')
+
+
+class TestNDArrayQunatityMath(QuantityTestCase):
+
+    @helpers.requires_numpy()
+    def test_exponentiation_array_exp(self):
+        arr = np.array(range(3), dtype=np.float)
+        q = self.Q_(arr, None)
+
+        for op_ in [op.pow, op.ipow]:
+            q_cp = copy.copy(q)
+            self.assertRaises(DimensionalityError, op_, 2., q_cp)
+            arr_cp = copy.copy(arr)
+            arr_cp = copy.copy(arr)
+            q_cp = copy.copy(q)
+            self.assertRaises(DimensionalityError, op_, q_cp, arr_cp)
+            q_cp = copy.copy(q)
+            q2_cp = copy.copy(q)
+            self.assertRaises(DimensionalityError, op_, q_cp, q2_cp)
+
+    @unittest.expectedFailure
+    @helpers.requires_numpy()
+    def test_exponentiation_array_exp_2(self):
+        arr = np.array(range(3), dtype=np.float)
+        #q = self.Q_(copy.copy(arr), None)
+        q = self.Q_(copy.copy(arr), 'meter')
+        arr_cp = copy.copy(arr)
+        q_cp = copy.copy(q)
+        # this fails as expected since numpy 1.8.0 but...
+        self.assertRaises(DimensionalityError, op.pow, arr_cp, q_cp)
+        # ..not for op.ipow !
+        # q_cp is treated as if it is an array. The units are ignored.
+        # _Quantity.__ipow__ is never called
+        arr_cp = copy.copy(arr)
+        q_cp = copy.copy(q)
+        self.assertRaises(DimensionalityError, op.ipow, arr_cp, q_cp)
 
=== modified file 'pint/testsuite/test_quantity.py'
--- pint/testsuite/test_quantity.py	2014-09-05 23:26:05 +0000
+++ pint/testsuite/test_quantity.py	2015-01-07 15:51:38 +0000
@@ -6,10 +6,11 @@
 import math
 import operator as op
 
-from pint import DimensionalityError, UnitRegistry
+from pint import DimensionalityError, OffsetUnitCalculusError, UnitRegistry
 from pint.unit import UnitsContainer
-from pint.compat import string_types, PYTHON3, np
+from pint.compat import string_types, PYTHON3, np, unittest
 from pint.testsuite import QuantityTestCase, helpers
+from pint.testsuite.parameterized import ParameterizedTestCase
 
 
 class TestQuantity(QuantityTestCase):
@@ -149,7 +150,7 @@
         # Conversions with single units take a different codepath than
         # Conversions with more than one unit.
         src_dst1 = UnitsContainer(meter=1), UnitsContainer(inch=1)
-        src_dst2 = UnitsContainer(meter=1, seconds=-1), UnitsContainer(inch=1, minutes=-1)
+        src_dst2 = UnitsContainer(meter=1, second=-1), UnitsContainer(inch=1, minute=-1)
         for src, dst in (src_dst1, src_dst2):
             a = np.ones((3, 1))
             ac = np.ones((3, 1))
@@ -209,14 +210,12 @@
 
 
     def test_offset_delta(self):
-        self.assertQuantityAlmostEqual(self.Q_(0, 'delta_kelvin').to('delta_kelvin'), self.Q_(0, 'delta_kelvin'))
-        self.assertQuantityAlmostEqual(self.Q_(0, 'delta_degC').to('delta_kelvin'), self.Q_(0, 'delta_kelvin'))
-        self.assertQuantityAlmostEqual(self.Q_(0, 'delta_degF').to('delta_kelvin'), self.Q_(0, 'delta_kelvin'), rtol=0.01)
+        self.assertQuantityAlmostEqual(self.Q_(0, 'delta_degC').to('kelvin'), self.Q_(0, 'kelvin'))
+        self.assertQuantityAlmostEqual(self.Q_(0, 'delta_degF').to('kelvin'), self.Q_(0, 'kelvin'), rtol=0.01)
 
-        self.assertQuantityAlmostEqual(self.Q_(100, 'delta_kelvin').to('delta_kelvin'), self.Q_(100, 'delta_kelvin'))
-        self.assertQuantityAlmostEqual(self.Q_(100, 'delta_kelvin').to('delta_degC'), self.Q_(100, 'delta_degC'))
-        self.assertQuantityAlmostEqual(self.Q_(100, 'delta_kelvin').to('delta_degF'), self.Q_(180, 'delta_degF'), rtol=0.01)
-        self.assertQuantityAlmostEqual(self.Q_(100, 'delta_degF').to('delta_kelvin'), self.Q_(55.55555556, 'delta_kelvin'), rtol=0.01)
+        self.assertQuantityAlmostEqual(self.Q_(100, 'kelvin').to('delta_degC'), self.Q_(100, 'delta_degC'))
+        self.assertQuantityAlmostEqual(self.Q_(100, 'kelvin').to('delta_degF'), self.Q_(180, 'delta_degF'), rtol=0.01)
+        self.assertQuantityAlmostEqual(self.Q_(100, 'delta_degF').to('kelvin'), self.Q_(55.55555556, 'kelvin'), rtol=0.01)
         self.assertQuantityAlmostEqual(self.Q_(100, 'delta_degC').to('delta_degF'), self.Q_(180, 'delta_degF'), rtol=0.01)
         self.assertQuantityAlmostEqual(self.Q_(100, 'delta_degF').to('delta_degC'), self.Q_(55.55555556, 'delta_degC'), rtol=0.01)
 
@@ -450,3 +449,547 @@
         from pint import _DEFAULT_REGISTRY
         cls.ureg = _DEFAULT_REGISTRY
         cls.Q_ = cls.ureg.Quantity
+
+
+class TestOffsetUnitMath(QuantityTestCase, ParameterizedTestCase):
+
+    def setup(self):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        self.ureg.default_as_delta = True
+
+    additions = [
+        # --- input tuple -------------------- | -- expected result --
+        (((100, 'kelvin'), (10, 'kelvin')),      (110, 'kelvin')),
+        (((100, 'kelvin'), (10, 'degC')),        'error'),
+        (((100, 'kelvin'), (10, 'degF')),        'error'),
+        (((100, 'kelvin'), (10, 'degR')),        (105.56, 'kelvin')),
+        (((100, 'kelvin'), (10, 'delta_degC')),  (110, 'kelvin')),
+        (((100, 'kelvin'), (10, 'delta_degF')),  (105.56, 'kelvin')),
+
+        (((100, 'degC'), (10, 'kelvin')),      'error'),
+        (((100, 'degC'), (10, 'degC')),        'error'),
+        (((100, 'degC'), (10, 'degF')),        'error'),
+        (((100, 'degC'), (10, 'degR')),        'error'),
+        (((100, 'degC'), (10, 'delta_degC')),  (110, 'degC')),
+        (((100, 'degC'), (10, 'delta_degF')),  (105.56, 'degC')),
+
+        (((100, 'degF'), (10, 'kelvin')),      'error'),
+        (((100, 'degF'), (10, 'degC')),        'error'),
+        (((100, 'degF'), (10, 'degF')),        'error'),
+        (((100, 'degF'), (10, 'degR')),        'error'),
+        (((100, 'degF'), (10, 'delta_degC')),  (118, 'degF')),
+        (((100, 'degF'), (10, 'delta_degF')),  (110, 'degF')),
+
+        (((100, 'degR'), (10, 'kelvin')),      (118, 'degR')),
+        (((100, 'degR'), (10, 'degC')),        'error'),
+        (((100, 'degR'), (10, 'degF')),        'error'),
+        (((100, 'degR'), (10, 'degR')),        (110, 'degR')),
+        (((100, 'degR'), (10, 'delta_degC')),  (118, 'degR')),
+        (((100, 'degR'), (10, 'delta_degF')),  (110, 'degR')),
+
+        (((100, 'delta_degC'), (10, 'kelvin')),     (110, 'kelvin')),
+        (((100, 'delta_degC'), (10, 'degC')),       (110, 'degC')),
+        (((100, 'delta_degC'), (10, 'degF')),       (190, 'degF')),
+        (((100, 'delta_degC'), (10, 'degR')),       (190, 'degR')),
+        (((100, 'delta_degC'), (10, 'delta_degC')), (110, 'delta_degC')),
+        (((100, 'delta_degC'), (10, 'delta_degF')), (105.56, 'delta_degC')),
+
+        (((100, 'delta_degF'), (10, 'kelvin')),     (65.56, 'kelvin')),
+        (((100, 'delta_degF'), (10, 'degC')),       (65.56, 'degC')),
+        (((100, 'delta_degF'), (10, 'degF')),       (110, 'degF')),
+        (((100, 'delta_degF'), (10, 'degR')),       (110, 'degR')),
+        (((100, 'delta_degF'), (10, 'delta_degC')), (118, 'delta_degF')),
+        (((100, 'delta_degF'), (10, 'delta_degF')), (110, 'delta_degF')),
+        ]
+
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        additions)
+    def test_addition(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        qin1, qin2 = input_tuple
+        q1, q2 = self.Q_(*qin1), self.Q_(*qin2)
+        # update input tuple with new values to have correct values on failure
+        input_tuple = q1, q2
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.add, q1, q2)
+        else:
+            expected = self.Q_(*expected)
+            self.assertEqual(op.add(q1, q2).units, expected.units)
+            self.assertQuantityAlmostEqual(op.add(q1, q2), expected,
+                                           atol=0.01)
+
+    @helpers.requires_numpy()
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        additions)
+    def test_inplace_addition(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        (q1v, q1u), (q2v, q2u) = input_tuple
+        # update input tuple with new values to have correct values on failure
+        input_tuple = ((np.array([q1v]*2, dtype=np.float), q1u),
+                       (np.array([q2v]*2, dtype=np.float), q2u))
+        Q_ = self.Q_
+        qin1, qin2 = input_tuple
+        q1, q2 = Q_(*qin1), Q_(*qin2)
+        q1_cp = copy.copy(q1)
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.iadd, q1_cp, q2)
+        else:
+            expected = np.array([expected[0]]*2, dtype=np.float), expected[1]
+            self.assertEqual(op.iadd(q1_cp, q2).units, Q_(*expected).units)
+            q1_cp = copy.copy(q1)
+            self.assertQuantityAlmostEqual(op.iadd(q1_cp, q2), Q_(*expected),
+                                           atol=0.01)
+
+    subtractions = [
+        (((100, 'kelvin'), (10, 'kelvin')),      (90, 'kelvin')),
+        (((100, 'kelvin'), (10, 'degC')),        (-183.15, 'kelvin')),
+        (((100, 'kelvin'), (10, 'degF')),        (-160.93, 'kelvin')),
+        (((100, 'kelvin'), (10, 'degR')),        (94.44, 'kelvin')),
+        (((100, 'kelvin'), (10, 'delta_degC')),  (90, 'kelvin')),
+        (((100, 'kelvin'), (10, 'delta_degF')),  (94.44, 'kelvin')),
+
+        (((100, 'degC'), (10, 'kelvin')),      (363.15, 'delta_degC')),
+        (((100, 'degC'), (10, 'degC')),        (90, 'delta_degC')),
+        (((100, 'degC'), (10, 'degF')),        (112.22, 'delta_degC')),
+        (((100, 'degC'), (10, 'degR')),        (367.59, 'delta_degC')),
+        (((100, 'degC'), (10, 'delta_degC')),  (90, 'degC')),
+        (((100, 'degC'), (10, 'delta_degF')),  (94.44, 'degC')),
+
+        (((100, 'degF'), (10, 'kelvin')),      (541.67, 'delta_degF')),
+        (((100, 'degF'), (10, 'degC')),        (50, 'delta_degF')),
+        (((100, 'degF'), (10, 'degF')),        (90, 'delta_degF')),
+        (((100, 'degF'), (10, 'degR')),        (549.67, 'delta_degF')),
+        (((100, 'degF'), (10, 'delta_degC')),  (82, 'degF')),
+        (((100, 'degF'), (10, 'delta_degF')),  (90, 'degF')),
+
+        (((100, 'degR'), (10, 'kelvin')),      (82, 'degR')),
+        (((100, 'degR'), (10, 'degC')),        (-409.67, 'degR')),
+        (((100, 'degR'), (10, 'degF')),        (-369.67, 'degR')),
+        (((100, 'degR'), (10, 'degR')),        (90, 'degR')),
+        (((100, 'degR'), (10, 'delta_degC')),  (82, 'degR')),
+        (((100, 'degR'), (10, 'delta_degF')),  (90, 'degR')),
+
+        (((100, 'delta_degC'), (10, 'kelvin')),     (90, 'kelvin')),
+        (((100, 'delta_degC'), (10, 'degC')),       (90, 'degC')),
+        (((100, 'delta_degC'), (10, 'degF')),       (170, 'degF')),
+        (((100, 'delta_degC'), (10, 'degR')),       (170, 'degR')),
+        (((100, 'delta_degC'), (10, 'delta_degC')), (90, 'delta_degC')),
+        (((100, 'delta_degC'), (10, 'delta_degF')), (94.44, 'delta_degC')),
+
+        (((100, 'delta_degF'), (10, 'kelvin')),     (45.56, 'kelvin')),
+        (((100, 'delta_degF'), (10, 'degC')),       (45.56, 'degC')),
+        (((100, 'delta_degF'), (10, 'degF')),       (90, 'degF')),
+        (((100, 'delta_degF'), (10, 'degR')),       (90, 'degR')),
+        (((100, 'delta_degF'), (10, 'delta_degC')), (82, 'delta_degF')),
+        (((100, 'delta_degF'), (10, 'delta_degF')), (90, 'delta_degF')),
+        ]
+
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        subtractions)
+    def test_subtraction(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        qin1, qin2 = input_tuple
+        q1, q2 = self.Q_(*qin1), self.Q_(*qin2)
+        input_tuple = q1, q2
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.sub, q1, q2)
+        else:
+            expected = self.Q_(*expected)
+            self.assertEqual(op.sub(q1, q2).units, expected.units)
+            self.assertQuantityAlmostEqual(op.sub(q1, q2), expected,
+                                           atol=0.01)
+
+#    @unittest.expectedFailure
+    @helpers.requires_numpy()
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        subtractions)
+    def test_inplace_subtraction(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        (q1v, q1u), (q2v, q2u) = input_tuple
+        # update input tuple with new values to have correct values on failure
+        input_tuple = ((np.array([q1v]*2, dtype=np.float), q1u),
+                       (np.array([q2v]*2, dtype=np.float), q2u))
+        Q_ = self.Q_
+        qin1, qin2 = input_tuple
+        q1, q2 = Q_(*qin1), Q_(*qin2)
+        q1_cp = copy.copy(q1)
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.isub, q1_cp, q2)
+        else:
+            expected = np.array([expected[0]]*2, dtype=np.float), expected[1]
+            self.assertEqual(op.isub(q1_cp, q2).units, Q_(*expected).units)
+            q1_cp = copy.copy(q1)
+            self.assertQuantityAlmostEqual(op.isub(q1_cp, q2), Q_(*expected),
+                                           atol=0.01)
+
+    multiplications = [
+        (((100, 'kelvin'), (10, 'kelvin')),     (1000, 'kelvin**2')),
+        (((100, 'kelvin'), (10, 'degC')),       'error'),
+        (((100, 'kelvin'), (10, 'degF')),       'error'),
+        (((100, 'kelvin'), (10, 'degR')),       (1000, 'kelvin*degR')),
+        (((100, 'kelvin'), (10, 'delta_degC')), (1000, 'kelvin*delta_degC')),
+        (((100, 'kelvin'), (10, 'delta_degF')), (1000, 'kelvin*delta_degF')),
+
+        (((100, 'degC'), (10, 'kelvin')),      'error'),
+        (((100, 'degC'), (10, 'degC')),        'error'),
+        (((100, 'degC'), (10, 'degF')),        'error'),
+        (((100, 'degC'), (10, 'degR')),        'error'),
+        (((100, 'degC'), (10, 'delta_degC')),  'error'),
+        (((100, 'degC'), (10, 'delta_degF')),  'error'),
+
+        (((100, 'degF'), (10, 'kelvin')),      'error'),
+        (((100, 'degF'), (10, 'degC')),        'error'),
+        (((100, 'degF'), (10, 'degF')),        'error'),
+        (((100, 'degF'), (10, 'degR')),        'error'),
+        (((100, 'degF'), (10, 'delta_degC')),  'error'),
+        (((100, 'degF'), (10, 'delta_degF')),  'error'),
+
+        (((100, 'degR'), (10, 'kelvin')),      (1000, 'degR*kelvin')),
+        (((100, 'degR'), (10, 'degC')),        'error'),
+        (((100, 'degR'), (10, 'degF')),        'error'),
+        (((100, 'degR'), (10, 'degR')),        (1000, 'degR**2')),
+        (((100, 'degR'), (10, 'delta_degC')),  (1000, 'degR*delta_degC')),
+        (((100, 'degR'), (10, 'delta_degF')),  (1000, 'degR*delta_degF')),
+
+        (((100, 'delta_degC'), (10, 'kelvin')),     (1000, 'delta_degC*kelvin')),
+        (((100, 'delta_degC'), (10, 'degC')),       'error'),
+        (((100, 'delta_degC'), (10, 'degF')),       'error'),
+        (((100, 'delta_degC'), (10, 'degR')),       (1000, 'delta_degC*degR')),
+        (((100, 'delta_degC'), (10, 'delta_degC')), (1000, 'delta_degC**2')),
+        (((100, 'delta_degC'), (10, 'delta_degF')), (1000, 'delta_degC*delta_degF')),
+
+        (((100, 'delta_degF'), (10, 'kelvin')),     (1000, 'delta_degF*kelvin')),
+        (((100, 'delta_degF'), (10, 'degC')),       'error'),
+        (((100, 'delta_degF'), (10, 'degF')),       'error'),
+        (((100, 'delta_degF'), (10, 'degR')),       (1000, 'delta_degF*degR')),
+        (((100, 'delta_degF'), (10, 'delta_degC')), (1000, 'delta_degF*delta_degC')),
+        (((100, 'delta_degF'), (10, 'delta_degF')), (1000, 'delta_degF**2')),
+        ]
+
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        multiplications)
+    def test_multiplication(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        qin1, qin2 = input_tuple
+        q1, q2 = self.Q_(*qin1), self.Q_(*qin2)
+        input_tuple = q1, q2
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.mul, q1, q2)
+        else:
+            expected = self.Q_(*expected)
+            self.assertEqual(op.mul(q1, q2).units, expected.units)
+            self.assertQuantityAlmostEqual(op.mul(q1, q2), expected,
+                                           atol=0.01)
+
+    @helpers.requires_numpy()
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        multiplications)
+    def test_inplace_multiplication(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        (q1v, q1u), (q2v, q2u) = input_tuple
+        # update input tuple with new values to have correct values on failure
+        input_tuple = ((np.array([q1v]*2, dtype=np.float), q1u),
+                       (np.array([q2v]*2, dtype=np.float), q2u))
+        Q_ = self.Q_
+        qin1, qin2 = input_tuple
+        q1, q2 = Q_(*qin1), Q_(*qin2)
+        q1_cp = copy.copy(q1)
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.imul, q1_cp, q2)
+        else:
+            expected = np.array([expected[0]]*2, dtype=np.float), expected[1]
+            self.assertEqual(op.imul(q1_cp, q2).units, Q_(*expected).units)
+            q1_cp = copy.copy(q1)
+            self.assertQuantityAlmostEqual(op.imul(q1_cp, q2), Q_(*expected),
+                                           atol=0.01)
+
+    divisions = [
+        (((100, 'kelvin'), (10, 'kelvin')),     (10, '')),
+        (((100, 'kelvin'), (10, 'degC')),       'error'),
+        (((100, 'kelvin'), (10, 'degF')),       'error'),
+        (((100, 'kelvin'), (10, 'degR')),       (10, 'kelvin/degR')),
+        (((100, 'kelvin'), (10, 'delta_degC')), (10, 'kelvin/delta_degC')),
+        (((100, 'kelvin'), (10, 'delta_degF')), (10, 'kelvin/delta_degF')),
+
+        (((100, 'degC'), (10, 'kelvin')),      'error'),
+        (((100, 'degC'), (10, 'degC')),        'error'),
+        (((100, 'degC'), (10, 'degF')),        'error'),
+        (((100, 'degC'), (10, 'degR')),        'error'),
+        (((100, 'degC'), (10, 'delta_degC')),  'error'),
+        (((100, 'degC'), (10, 'delta_degF')),  'error'),
+
+        (((100, 'degF'), (10, 'kelvin')),      'error'),
+        (((100, 'degF'), (10, 'degC')),        'error'),
+        (((100, 'degF'), (10, 'degF')),        'error'),
+        (((100, 'degF'), (10, 'degR')),        'error'),
+        (((100, 'degF'), (10, 'delta_degC')),  'error'),
+        (((100, 'degF'), (10, 'delta_degF')),  'error'),
+
+        (((100, 'degR'), (10, 'kelvin')),      (10, 'degR/kelvin')),
+        (((100, 'degR'), (10, 'degC')),        'error'),
+        (((100, 'degR'), (10, 'degF')),        'error'),
+        (((100, 'degR'), (10, 'degR')),        (10, '')),
+        (((100, 'degR'), (10, 'delta_degC')),  (10, 'degR/delta_degC')),
+        (((100, 'degR'), (10, 'delta_degF')),  (10, 'degR/delta_degF')),
+
+        (((100, 'delta_degC'), (10, 'kelvin')),     (10, 'delta_degC/kelvin')),
+        (((100, 'delta_degC'), (10, 'degC')),       'error'),
+        (((100, 'delta_degC'), (10, 'degF')),       'error'),
+        (((100, 'delta_degC'), (10, 'degR')),       (10, 'delta_degC/degR')),
+        (((100, 'delta_degC'), (10, 'delta_degC')), (10, '')),
+        (((100, 'delta_degC'), (10, 'delta_degF')), (10, 'delta_degC/delta_degF')),
+
+        (((100, 'delta_degF'), (10, 'kelvin')),     (10, 'delta_degF/kelvin')),
+        (((100, 'delta_degF'), (10, 'degC')),       'error'),
+        (((100, 'delta_degF'), (10, 'degF')),       'error'),
+        (((100, 'delta_degF'), (10, 'degR')),       (10, 'delta_degF/degR')),
+        (((100, 'delta_degF'), (10, 'delta_degC')), (10, 'delta_degF/delta_degC')),
+        (((100, 'delta_degF'), (10, 'delta_degF')), (10, '')),
+        ]
+
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        divisions)
+    def test_truedivision(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        qin1, qin2 = input_tuple
+        q1, q2 = self.Q_(*qin1), self.Q_(*qin2)
+        input_tuple = q1, q2
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.truediv, q1, q2)
+        else:
+            expected = self.Q_(*expected)
+            self.assertEqual(op.truediv(q1, q2).units, expected.units)
+            self.assertQuantityAlmostEqual(op.truediv(q1, q2), expected,
+                                           atol=0.01)
+
+    @helpers.requires_numpy()
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        divisions)
+    def test_inplace_truedivision(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = False
+        (q1v, q1u), (q2v, q2u) = input_tuple
+        # update input tuple with new values to have correct values on failure
+        input_tuple = ((np.array([q1v]*2, dtype=np.float), q1u),
+                       (np.array([q2v]*2, dtype=np.float), q2u))
+        Q_ = self.Q_
+        qin1, qin2 = input_tuple
+        q1, q2 = Q_(*qin1), Q_(*qin2)
+        q1_cp = copy.copy(q1)
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.itruediv, q1_cp, q2)
+        else:
+            expected = np.array([expected[0]]*2, dtype=np.float), expected[1]
+            self.assertEqual(op.itruediv(q1_cp, q2).units, Q_(*expected).units)
+            q1_cp = copy.copy(q1)
+            self.assertQuantityAlmostEqual(op.itruediv(q1_cp, q2),
+                                           Q_(*expected), atol=0.01)
+
+    multiplications_with_autoconvert_to_baseunit = [
+        (((100, 'kelvin'), (10, 'degC')),     (28315., 'kelvin**2')),
+        (((100, 'kelvin'), (10, 'degF')),     (26092.78, 'kelvin**2')),
+
+        (((100, 'degC'), (10, 'kelvin')),     (3731.5, 'kelvin**2')),
+        (((100, 'degC'), (10, 'degC')),       (105657.42, 'kelvin**2')),
+        (((100, 'degC'), (10, 'degF')),       (97365.20, 'kelvin**2')),
+        (((100, 'degC'), (10, 'degR')),       (3731.5, 'kelvin*degR')),
+        (((100, 'degC'), (10, 'delta_degC')), (3731.5, 'kelvin*delta_degC')),
+        (((100, 'degC'), (10, 'delta_degF')), (3731.5, 'kelvin*delta_degF')),
+
+        (((100, 'degF'), (10, 'kelvin')),     (3109.28, 'kelvin**2')),
+        (((100, 'degF'), (10, 'degC')),       (88039.20, 'kelvin**2')),
+        (((100, 'degF'), (10, 'degF')),       (81129.69, 'kelvin**2')),
+        (((100, 'degF'), (10, 'degR')),       (3109.28, 'kelvin*degR')),
+        (((100, 'degF'), (10, 'delta_degC')), (3109.28, 'kelvin*delta_degC')),
+        (((100, 'degF'), (10, 'delta_degF')), (3109.28, 'kelvin*delta_degF')),
+
+        (((100, 'degR'), (10, 'degC')),       (28315., 'degR*kelvin')),
+        (((100, 'degR'), (10, 'degF')),       (26092.78, 'degR*kelvin')),
+
+        (((100, 'delta_degC'), (10, 'degC')), (28315., 'delta_degC*kelvin')),
+        (((100, 'delta_degC'), (10, 'degF')), (26092.78, 'delta_degC*kelvin')),
+
+        (((100, 'delta_degF'), (10, 'degC')), (28315., 'delta_degF*kelvin')),
+        (((100, 'delta_degF'), (10, 'degF')), (26092.78, 'delta_degF*kelvin')),
+        ]
+
+    @ParameterizedTestCase.parameterize(
+        ("input", "expected_output"),
+        multiplications_with_autoconvert_to_baseunit)
+    def test_multiplication_with_autoconvert(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = True
+        qin1, qin2 = input_tuple
+        q1, q2 = self.Q_(*qin1), self.Q_(*qin2)
+        input_tuple = q1, q2
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.mul, q1, q2)
+        else:
+            expected = self.Q_(*expected)
+            self.assertEqual(op.mul(q1, q2).units, expected.units)
+            self.assertQuantityAlmostEqual(op.mul(q1, q2), expected,
+                                           atol=0.01)
+
+    @helpers.requires_numpy()
+    @ParameterizedTestCase.parameterize(
+        ("input", "expected_output"),
+        multiplications_with_autoconvert_to_baseunit)
+    def test_inplace_multiplication_with_autoconvert(self, input_tuple, expected):
+        self.ureg.autoconvert_offset_to_baseunit = True
+        (q1v, q1u), (q2v, q2u) = input_tuple
+        # update input tuple with new values to have correct values on failure
+        input_tuple = ((np.array([q1v]*2, dtype=np.float), q1u),
+                       (np.array([q2v]*2, dtype=np.float), q2u))
+        Q_ = self.Q_
+        qin1, qin2 = input_tuple
+        q1, q2 = Q_(*qin1), Q_(*qin2)
+        q1_cp = copy.copy(q1)
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.imul, q1_cp, q2)
+        else:
+            expected = np.array([expected[0]]*2, dtype=np.float), expected[1]
+            self.assertEqual(op.imul(q1_cp, q2).units, Q_(*expected).units)
+            q1_cp = copy.copy(q1)
+            self.assertQuantityAlmostEqual(op.imul(q1_cp, q2), Q_(*expected),
+                                           atol=0.01)
+
+    multiplications_with_scalar = [
+        (((10, 'kelvin'),    2),    (20., 'kelvin')),
+        (((10, 'kelvin**2'), 2),    (20., 'kelvin**2')),
+        (((10, 'degC'),      2),    (20., 'degC')),
+        (((10, '1/degC'),    2),    'error'),
+        (((10, 'degC**0.5'),   2),  'error'),
+        (((10, 'degC**2'),   2),    'error'),
+        (((10, 'degC**-2'),  2),    'error'),
+        ]
+
+    @ParameterizedTestCase.parameterize(
+        ("input", "expected_output"), multiplications_with_scalar)
+    def test_multiplication_with_scalar(self, input_tuple, expected):
+        self.ureg.default_as_delta = False
+        in1, in2 = input_tuple
+        if type(in1) is tuple:
+            in1, in2 = self.Q_(*in1), in2
+        else:
+            in1, in2 = in1, self.Q_(*in2)
+        input_tuple = in1, in2  # update input_tuple for better tracebacks
+        if expected == 'error':
+            self.assertRaises(OffsetUnitCalculusError, op.mul, in1, in2)
+        else:
+            expected = self.Q_(*expected)
+            self.assertEqual(op.mul(in1, in2).units, expected.units)
+            self.assertQuantityAlmostEqual(op.mul(in1, in2), expected,
+                                           atol=0.01)
+
+    divisions_with_scalar = [   # without / with autoconvert to base unit
+        (((10, 'kelvin'), 2),       [(5., 'kelvin'), (5., 'kelvin')]),
+        (((10, 'kelvin**2'), 2),    [(5., 'kelvin**2'), (5., 'kelvin**2')]),
+        (((10, 'degC'), 2),         ['error', 'error']),
+        (((10, 'degC**2'), 2),      ['error', 'error']),
+        (((10, 'degC**-2'), 2),     ['error', 'error']),
+
+        ((2, (10, 'kelvin')),       [(0.2, '1/kelvin'), (0.2, '1/kelvin')]),
+        ((2, (10, 'degC')),         ['error', (2/283.15, '1/kelvin')]),
+        ((2, (10, 'degC**2')),      ['error', 'error']),
+        ((2, (10, 'degC**-2')),     ['error', 'error']),
+        ]
+
+    @ParameterizedTestCase.parameterize(
+        ("input", "expected_output"), divisions_with_scalar)
+    def test_division_with_scalar(self, input_tuple, expected):
+        self.ureg.default_as_delta = False
+        in1, in2 = input_tuple
+        if type(in1) is tuple:
+            in1, in2 = self.Q_(*in1), in2
+        else:
+            in1, in2 = in1, self.Q_(*in2)
+        input_tuple = in1, in2  # update input_tuple for better tracebacks
+        expected_copy = expected[:]
+        for i, mode in enumerate([False, True]):
+            self.ureg.autoconvert_offset_to_baseunit = mode
+            if expected_copy[i] == 'error':
+                self.assertRaises(OffsetUnitCalculusError, op.truediv, in1, in2)
+            else:
+                expected = self.Q_(*expected_copy[i])
+                self.assertEqual(op.truediv(in1, in2).units, expected.units)
+                self.assertQuantityAlmostEqual(op.truediv(in1, in2), expected)
+
+    exponentiation = [                  # resuls without / with autoconvert
+        (((10, 'degC'),    1),          [(10, 'degC'), (10, 'degC')]),
+        (((10, 'degC'),    0.5),        ['error', (283.15**0.5, 'kelvin**0.5')]),
+        (((10, 'degC'),    0),          [(1., ''), (1., '')]),
+        (((10, 'degC'),   -1),          ['error', (1/(10+273.15), 'kelvin**-1')]),
+        (((10, 'degC'),   -2),          ['error', (1/(10+273.15)**2., 'kelvin**-2')]),
+        ((( 0, 'degC'),   -2),          ['error', (1/(273.15)**2, 'kelvin**-2')]),
+        (((10, 'degC'),   (2, '')),     ['error', ((283.15)**2, 'kelvin**2')]),
+        (((10, 'degC'),  (10, 'degK')), ['error', 'error']),
+
+        (((10, 'kelvin'), (2, '')),     [(100., 'kelvin**2'), (100., 'kelvin**2')]),
+
+        ((  2,          (2, 'kelvin')), ['error', 'error']),
+        ((  2,          (500., 'millikelvin/kelvin')), [2**0.5, 2**0.5]),
+        ((  2,          (0.5, 'kelvin/kelvin')),      [2**0.5, 2**0.5]),
+        (((10, 'degC'), (500., 'millikelvin/kelvin')),
+                                        ['error', (283.15**0.5, 'kelvin**0.5')]),
+         ]
+
+    @ParameterizedTestCase.parameterize(
+        ("input", "expected_output"), exponentiation)
+    def test_exponentiation(self, input_tuple, expected):
+        self.ureg.default_as_delta = False
+        in1, in2 = input_tuple
+        if type(in1) is tuple and type(in2) is tuple:
+            in1, in2 = self.Q_(*in1), self.Q_(*in2)
+        elif not type(in1) is tuple and type(in2) is tuple:
+            in2 = self.Q_(*in2)
+        else:
+            in1 = self.Q_(*in1)
+        input_tuple = in1, in2
+        expected_copy = expected[:]
+        for i, mode in enumerate([False, True]):
+            self.ureg.autoconvert_offset_to_baseunit = mode
+            if expected_copy[i] == 'error':
+                self.assertRaises((OffsetUnitCalculusError,
+                                   DimensionalityError), op.pow, in1, in2)
+            else:
+                if type(expected_copy[i]) is tuple:
+                    expected = self.Q_(*expected_copy[i])
+                    self.assertEqual(op.pow(in1, in2).units, expected.units)
+                else:
+                    expected = expected_copy[i]
+                self.assertQuantityAlmostEqual(op.pow(in1, in2), expected)
+
+    @helpers.requires_numpy()
+    @ParameterizedTestCase.parameterize(
+        ("input", "expected_output"), exponentiation)
+    def test_inplace_exponentiation(self, input_tuple, expected):
+        self.ureg.default_as_delta = False
+        in1, in2 = input_tuple
+        if type(in1) is tuple and type(in2) is tuple:
+            (q1v, q1u), (q2v, q2u) = in1, in2
+            in1 = self.Q_(*(np.array([q1v]*2, dtype=np.float), q1u))
+            in2 = self.Q_(q2v, q2u)
+        elif not type(in1) is tuple and type(in2) is tuple:
+            in2 = self.Q_(*in2)
+        else:
+            in1 = self.Q_(*in1)
+
+        input_tuple = in1, in2
+
+        expected_copy = expected[:]
+        for i, mode in enumerate([False, True]):
+            self.ureg.autoconvert_offset_to_baseunit = mode
+            in1_cp = copy.copy(in1)
+            if expected_copy[i] == 'error':
+                self.assertRaises((OffsetUnitCalculusError,
+                                   DimensionalityError), op.ipow, in1_cp, in2)
+            else:
+                if type(expected_copy[i]) is tuple:
+                    expected = self.Q_(np.array([expected_copy[i][0]]*2,
+                                                dtype=np.float),
+                                       expected_copy[i][1])
+                    self.assertEqual(op.ipow(in1_cp, in2).units, expected.units)
+                else:
+                    expected = np.array([expected_copy[i]]*2, dtype=np.float)
+
+
+                in1_cp = copy.copy(in1)
+                self.assertQuantityAlmostEqual(op.ipow(in1_cp, in2), expected)
 
=== modified file 'pint/testsuite/test_umath.py'
--- pint/testsuite/test_umath.py	2014-09-05 23:26:05 +0000
+++ pint/testsuite/test_umath.py	2015-01-07 15:51:38 +0000
@@ -52,17 +52,29 @@
         except Exception as e:
             self.assertFalse(True, msg='{0} not raised but {1}\n{2}'.format(ExcType, e, msg))
 
-    def _testn(self, func,  ok_with, raise_with=(), results=None):
-        self._test1(func, ok_with, raise_with, output_units=None, results=results)
-
     def _test1(self, func,  ok_with, raise_with=(), output_units='same', results=None, rtol=1e-6):
+        """Test function that takes a single argument and returns Quantity.
+
+        :param func: function callable.
+        :param ok_with: iterables of values that work fine.
+        :param raise_with: iterables of values that raise exceptions.
+        :param output_units: units to be used when building results.
+                             'same': ok_with[n].units (default).
+                             is float: ok_with[n].units ** output_units.
+                             None: no output units, the result should be an ndarray.
+                             Other value will be parsed as unit.
+        :param results: iterable of results.
+                        If None, the result will be obtained by applying
+                        func to each ok_with value
+        :param rtol: relative tolerance.
+        """
         if results is None:
             results = [None, ] * len(ok_with)
         for x1, res in zip(ok_with, results):
             err_msg = 'At {0} with {1}'.format(func.__name__, x1)
             if output_units == 'same':
                 ou = x1.units
-            elif isinstance(output_units, int):
+            elif isinstance(output_units, (int, float)):
                 ou = x1.units ** output_units
             else:
                 ou = output_units
@@ -70,20 +82,45 @@
             qm = func(x1)
             if res is None:
                 res = func(x1.magnitude)
-                if ou:
+                if ou is not None:
                     res = self.Q_(res, ou)
-            if isinstance(res, self.Q_):
-                self.assertIsInstance(qm, self.Q_, msg=err_msg + ' {0!r} is not Quantity'.format(qm))
-                qm = qm.magnitude
-                res = res.magnitude
-            np.testing.assert_allclose(qm, res, rtol=rtol, err_msg=err_msg)
+
+            self.assertQuantityAlmostEqual(qm, res, rtol=rtol, msg=err_msg)
 
         for x1 in raise_with:
             self.assertRaisesMsg('At {0} with {1}'.format(func.__name__, x1),
                                  ValueError, func, x1)
 
+    def _testn(self, func,  ok_with, raise_with=(), results=None):
+        """Test function that takes a single argument and returns and ndarray (not a Quantity)
+
+        :param func: function callable.
+        :param ok_with: iterables of values that work fine.
+        :param raise_with: iterables of values that raise exceptions.
+        :param results: iterable of results.
+                        If None, the result will be obtained by applying
+                        func to each ok_with value
+        """
+        self._test1(func, ok_with, raise_with, output_units=None, results=results)
+
     def _test1_2o(self, func, ok_with, raise_with=(), output_units=('same', 'same'),
                   results=None, rtol=1e-6):
+        """Test functions that takes a single argument and return two Quantities.
+
+        :param func: function callable.
+        :param ok_with: iterables of values that work fine.
+        :param raise_with: iterables of values that raise exceptions.
+        :param output_units: tuple of units to be used when building the result tuple.
+                             'same': ok_with[n].units (default).
+                             is float: ok_with[n].units ** output_units.
+                             None: no output units, the result should be an ndarray.
+                             Other value will be parsed as unit.
+        :param results: iterable of results.
+                        If None, the result will be obtained by applying
+                        func to each ok_with value
+        :param rtol: relative tolerance.
+        """
+
         if results is None:
             results = [None, ] * len(ok_with)
         for x1, res in zip(ok_with, results):
@@ -95,26 +132,35 @@
             for ndx, (qm, re, ou) in enumerate(zip(qms, res, output_units)):
                 if ou == 'same':
                     ou = x1.units
-                elif isinstance(ou, int):
+                elif isinstance(ou, (int, float)):
                     ou = x1.units ** ou
 
                 if ou is not None:
                     re = self.Q_(re, ou)
 
-                if isinstance(re, self.Q_):
-                    self.assertIsInstance(qm, self.Q_, msg=err_msg)
-                    qm = qm.magnitude
-                    re = re.magnitude
-                np.testing.assert_allclose(qm, re, rtol=rtol, err_msg=err_msg)
+                self.assertQuantityAlmostEqual(qm, re, rtol=rtol, msg=err_msg)
 
         for x1 in raise_with:
             self.assertRaisesMsg('At {0} with {1}'.format(func.__name__, x1),
                                  ValueError, func, x1)
 
-    def _testn2(self, func, x1, ok_with, raise_with=()):
-        self._test2(func, x1, ok_with, raise_with, output_units=None)
-
     def _test2(self, func, x1, ok_with, raise_with=(), output_units='same', rtol=1e-6, convert2=True):
+        """Test function that takes two arguments and return a Quantity.
+
+        :param func: function callable.
+        :param x1: first argument of func.
+        :param ok_with: iterables of values that work fine.
+        :param raise_with: iterables of values that raise exceptions.
+        :param output_units: units to be used when building results.
+                             'same': x1.units (default).
+                             'prod': x1.units * ok_with[n].units
+                             'div': x1.units / ok_with[n].units
+                             'second': x1.units * ok_with[n]
+                             None: no output units, the result should be an ndarray.
+                             Other value will be parsed as unit.
+        :param rtol: relative tolerance.
+        :param convert2: if the ok_with[n] should be converted to x1.units.
+        """
         for x2 in ok_with:
             err_msg = 'At {0} with {1} and {2}'.format(func.__name__, x1, x2)
             if output_units == 'same':
@@ -136,18 +182,25 @@
                 m2 = getattr(x2, 'magnitude', x2)
 
             res = func(x1.magnitude, m2)
-            if ou:
+            if ou is not None:
                 res = self.Q_(res, ou)
-            if isinstance(res, self.Q_):
-                self.assertIsInstance(qm, self.Q_, msg=err_msg)
-                qm = qm.magnitude
-                res = res.magnitude
-            np.testing.assert_allclose(qm, res, rtol=rtol, err_msg=err_msg)
+
+            self.assertQuantityAlmostEqual(qm, res, rtol=rtol, msg=err_msg)
 
         for x2 in raise_with:
             self.assertRaisesMsg('At {0} with {1} and {2}'.format(func.__name__, x1, x2),
                                  ValueError, func, x1, x2)
 
+    def _testn2(self, func, x1, ok_with, raise_with=()):
+        """Test function that takes two arguments and return a ndarray.
+
+        :param func: function callable.
+        :param x1: first argument of func.
+        :param ok_with: iterables of values that work fine.
+        :param raise_with: iterables of values that raise exceptions.
+        """
+        self._test2(func, x1, ok_with, raise_with, output_units=None)
+
 
 @helpers.requires_numpy()
 class TestMathUfuncs(TestUFuncs):
@@ -248,7 +301,7 @@
                     self.q1,
                     (self.q2, self.qs, self.qless),
                     (),
-                    'div', convert2=False)
+                    'same', convert2=False)
 
     def test_mod(self):
         self._test2(np.mod,
@@ -322,7 +375,7 @@
         self._test1(np.sqrt,
                     (self.q2, self.qs, self.qless, self.qi),
                     (),
-                    'same')
+                    0.5)
 
     def test_square(self):
         self._test1(np.square,
@@ -334,7 +387,7 @@
         self._test1(np.reciprocal,
                     (self.q2, self.qs, self.qless, self.qi),
                     (),
-                    2)
+                    -1)
 
 
 @helpers.requires_numpy()
@@ -469,10 +522,16 @@
                                  ), (self.ureg.m, ), 'radians')
 
     def test_rad2deg(self):
-        self._test1(np.rad2deg, (np.arange(0, pi/2, pi/4) * self.ureg.dimensionless,
-                                 np.arange(0, pi/2, pi/4) * self.ureg.radian,
-                                 np.arange(0, pi/2, pi/4) * self.ureg.mm / self.ureg.m
-                                 ), (self.ureg.m, ), 'degree', results=(None, None, np.rad2deg(np.arange(0, pi/2, pi/4)*0.001)))
+        self._test1(np.rad2deg,
+                    (np.arange(0, pi/2, pi/4) * self.ureg.dimensionless,
+                     np.arange(0, pi/2, pi/4) * self.ureg.radian,
+                     np.arange(0, pi/2, pi/4) * self.ureg.mm / self.ureg.m,
+                     ),
+                    (self.ureg.m, ), 'degree',
+                    results=(None,
+                             None,
+                             np.rad2deg(np.arange(0, pi/2, pi/4)*0.001) * self.ureg.degree,
+                    ))
 
 
 
 
=== modified file 'pint/testsuite/test_unit.py'
--- pint/testsuite/test_unit.py	2014-09-05 23:26:05 +0000
+++ pint/testsuite/test_unit.py	2015-01-07 15:51:38 +0000
@@ -12,8 +12,9 @@
                        DimensionDefinition, _freeze, Converter, UnitRegistry,
                        LazyRegistry, ParserHelper)
 from pint import DimensionalityError, UndefinedUnitError
-from pint.compat import u, unittest, np
+from pint.compat import u, unittest, np, string_types
 from pint.testsuite import QuantityTestCase, helpers, BaseTestCase
+from pint.testsuite.parameterized import ParameterizedTestCase
 
 
 class TestConverter(BaseTestCase):
@@ -231,6 +232,9 @@
 
     FORCE_NDARRAY = False
 
+    def setup(self):
+        self.ureg.autoconvert_offset_to_baseunit = False
+
     def test_base(self):
         ureg = UnitRegistry(None)
         ureg.define('meter = [length]')
@@ -324,16 +328,16 @@
         q = self.Q_(1, 'g/(m**2*s)')
         self.assertEqual(self.Q_(q.magnitude, str(q.units)), q)
 
-    def test_to_delta(self):
+    def test_as_delta(self):
         parse = self.ureg.parse_units
-        self.assertEqual(parse('kelvin', to_delta=True), UnitsContainer(kelvin=1))
-        self.assertEqual(parse('kelvin', to_delta=False), UnitsContainer(kelvin=1))
-        self.assertEqual(parse('kelvin**(-1)', to_delta=True), UnitsContainer(kelvin=-1))
-        self.assertEqual(parse('kelvin**(-1)', to_delta=False), UnitsContainer(kelvin=-1))
-        self.assertEqual(parse('kelvin**2', to_delta=True), UnitsContainer(kelvin=2))
-        self.assertEqual(parse('kelvin**2', to_delta=False), UnitsContainer(kelvin=2))
-        self.assertEqual(parse('kelvin*meter', to_delta=True), UnitsContainer(kelvin=1, meter= 1))
-        self.assertEqual(parse('kelvin*meter', to_delta=False), UnitsContainer(kelvin=1, meter=1))
+        self.assertEqual(parse('kelvin', as_delta=True), UnitsContainer(kelvin=1))
+        self.assertEqual(parse('kelvin', as_delta=False), UnitsContainer(kelvin=1))
+        self.assertEqual(parse('kelvin**(-1)', as_delta=True), UnitsContainer(kelvin=-1))
+        self.assertEqual(parse('kelvin**(-1)', as_delta=False), UnitsContainer(kelvin=-1))
+        self.assertEqual(parse('kelvin**2', as_delta=True), UnitsContainer(kelvin=2))
+        self.assertEqual(parse('kelvin**2', as_delta=False), UnitsContainer(kelvin=2))
+        self.assertEqual(parse('kelvin*meter', as_delta=True), UnitsContainer(kelvin=1, meter= 1))
+        self.assertEqual(parse('kelvin*meter', as_delta=False), UnitsContainer(kelvin=1, meter=1))
 
     def test_name(self):
         self.assertRaises(UndefinedUnitError, self.ureg.get_name, 'asdf')
@@ -357,18 +361,6 @@
         self.assertEqual(self.ureg.get_symbol('international_foot'), 'ft')
         self.assertEqual(self.ureg.get_symbol('international_inch'), 'in')
 
-    @unittest.expectedFailure
-    def test_delta_in_diff(self):
-        """This might be supported in future versions
-        """
-        xk = 1 * self.ureg.kelvin
-        yk = 2 * self.ureg.kelvin
-        yf = yk.to('degF')
-        yc = yk.to('degC')
-        self.assertEqual(yk - xk, 1 * self.ureg.kelvin)
-        self.assertEqual(yf - xk, 1 * self.ureg.kelvin)
-        self.assertEqual(yc - xk, 1 * self.ureg.kelvin)
-
     def test_pint(self):
         p = self.ureg.pint
         l = self.ureg.liter
@@ -440,12 +432,13 @@
         self.assertEqual(h2(3, 1), (3 * ureg.meter, 1 * ureg.cm))
 
     def test_to_ref_vs_to(self):
+        self.ureg.autoconvert_offset_to_baseunit = True
         q = 8. * self.ureg.inch
         t = 8. * self.ureg.degF
         dt = 8. * self.ureg.delta_degF
         self.assertEqual(q.to('cm').magnitude, self.ureg._units['inch'].converter.to_reference(8.))
         self.assertEqual(t.to('kelvin').magnitude, self.ureg._units['degF'].converter.to_reference(8.))
-        self.assertEqual(dt.to('delta_kelvin').magnitude, self.ureg._units['delta_degF'].converter.to_reference(8.))
+        self.assertEqual(dt.to('kelvin').magnitude, self.ureg._units['delta_degF'].converter.to_reference(8.))
 
     def test_redefinition(self):
         d = UnitRegistry().define
@@ -473,7 +466,7 @@
         # Conversions with single units take a different codepath than
         # Conversions with more than one unit.
         src_dst1 = UnitsContainer(meter=1), UnitsContainer(inch=1)
-        src_dst2 = UnitsContainer(meter=1, seconds=-1), UnitsContainer(inch=1, minutes=-1)
+        src_dst2 = UnitsContainer(meter=1, second=-1), UnitsContainer(inch=1, minute=-1)
         for src, dst in (src_dst1, src_dst2):
             v = ureg.convert(1, src, dst),
 
@@ -598,3 +591,52 @@
         msg = "Cannot convert from 'a' (c) to 'b' (d)msg"
         ex = DimensionalityError('a', 'b', 'c', 'd', 'msg')
         self.assertEqual(str(ex), msg)
+
+
+class TestConvertWithOffset(QuantityTestCase, ParameterizedTestCase):
+
+    # The dicts in convert_with_offset are used to create a UnitsContainer.
+    # We create UnitsContainer to avoid any auto-conversion of units.
+    convert_with_offset = [
+        (({'degC': 1}, {'degC': 1}), 10),
+        (({'degC': 1}, {'kelvin': 1}), 283.15),
+        (({'degC': 1}, {'degC': 1, 'millimeter': 1, 'meter': -1}), 'error'),
+        (({'degC': 1}, {'kelvin': 1, 'millimeter': 1, 'meter': -1}), 283150),
+
+        (({'kelvin': 1}, {'degC': 1}), -263.15),
+        (({'kelvin': 1}, {'kelvin': 1}), 10),
+        (({'kelvin': 1}, {'degC': 1, 'millimeter': 1, 'meter': -1}), 'error'),
+        (({'kelvin': 1}, {'kelvin': 1, 'millimeter': 1, 'meter': -1}), 10000),
+
+        (({'degC': 1, 'millimeter': 1, 'meter': -1}, {'degC': 1}), 'error'),
+        (({'degC': 1, 'millimeter': 1, 'meter': -1}, {'kelvin': 1}), 'error'),
+        (({'degC': 1, 'millimeter': 1, 'meter': -1}, {'degC': 1, 'millimeter': 1, 'meter': -1}), 10),
+        (({'degC': 1, 'millimeter': 1, 'meter': -1}, {'kelvin': 1, 'millimeter': 1, 'meter': -1}), 'error'),
+
+        (({'kelvin': 1, 'millimeter': 1, 'meter': -1}, {'degC': 1}), -273.14),
+        (({'kelvin': 1, 'millimeter': 1, 'meter': -1}, {'kelvin': 1}), 0.01),
+        (({'kelvin': 1, 'millimeter': 1, 'meter': -1}, {'degC': 1, 'millimeter': 1, 'meter': -1}), 'error'),
+        (({'kelvin': 1, 'millimeter': 1, 'meter': -1}, {'kelvin': 1, 'millimeter': 1, 'meter': -1}), 10),
+
+        (({'degC': 2}, {'kelvin': 2}), 'error'),
+        (({'degC': 1, 'degF': 1}, {'kelvin': 2}), 'error'),
+        (({'degC': 1, 'kelvin': 1}, {'kelvin': 2}), 'error'),
+        ]
+
+    @ParameterizedTestCase.parameterize(("input", "expected_output"),
+                                        convert_with_offset)
+    def test_to_and_from_offset_units(self, input_tuple, expected):
+        src, dst = input_tuple
+        src, dst = UnitsContainer(src), UnitsContainer(dst)
+        value = 10.
+        convert = self.ureg.convert
+        if isinstance(expected, string_types):
+            self.assertRaises(DimensionalityError, convert, value, src, dst)
+            if src != dst:
+                self.assertRaises(DimensionalityError, convert, value, dst, src)
+        else:
+            self.assertQuantityAlmostEqual(convert(value, src, dst),
+                                           expected, atol=0.001)
+            if src != dst:
+                self.assertQuantityAlmostEqual(convert(expected, dst, src),
+                                               value, atol=0.001)
 
=== modified file 'pint/unit.py'
--- pint/unit.py	2014-09-05 23:26:05 +0000
+++ pint/unit.py	2015-01-07 15:51:38 +0000
@@ -87,7 +87,7 @@
     """Raised when trying to convert between incompatible units.
     """
 
-    def __init__(self, units1, units2, dim1=None, dim2=None, extra_msg=None):
+    def __init__(self, units1, units2, dim1=None, dim2=None, extra_msg=''):
         super(DimensionalityError, self).__init__()
         self.units1 = units1
         self.units2 = units2
@@ -103,12 +103,25 @@
             dim1 = ''
             dim2 = ''
 
-        msg = "Cannot convert from '{0}'{1} to '{2}'{3}".format(self.units1, dim1, self.units2, dim2)
-
-        if self.extra_msg:
-            return msg + self.extra_msg
-
-        return msg
+        msg = "Cannot convert from '{0}'{1} to '{2}'{3}" + self.extra_msg
+
+        return msg.format(self.units1, dim1, self.units2, dim2)
+
+
+class OffsetUnitCalculusError(ValueError):
+    """Raised on ambiguous operations with offset units.
+    """
+    def __init__(self, units1, units2='', extra_msg=''):
+        super(ValueError, self).__init__()
+        self.units1 = units1
+        self.units2 = units2
+        self.extra_msg = extra_msg
+
+    def __str__(self):
+        msg = ("Ambiguous operation with offset unit (%s)." %
+               ', '.join(['%s' % u for u in [self.units1, self.units2] if u])
+               + self.extra_msg)
+        return msg.format(self.units1, self.units2)
 
 
 class Converter(object):
@@ -244,7 +257,7 @@
 
 
 def _is_dim(name):
-    return name.startswith('[') and name.endswith(']')
+    return name[0] == '[' and name[-1] == ']'
 
 
 class PrefixDefinition(Definition):
@@ -289,7 +302,7 @@
                                  'Base units must be referenced only to dimensions. '
                                  'Derived units must be referenced only to units.')
             self.reference = UnitsContainer(converter.items())
-            if 'offset' in modifiers:
+            if modifiers.get('offset', 0.) != 0.:
                 converter = OffsetConverter(converter.scale, modifiers['offset'])
             else:
                 converter = ScaleConverter(converter.scale)
@@ -445,14 +458,19 @@
                      Empty to load the default definition file.
                      None to leave the UnitRegistry empty.
     :param force_ndarray: convert any input, scalar or not to a numpy.ndarray.
-    :param default_to_delta: In the context of a multiplication of units, interpret
+    :param default_as_delta: In the context of a multiplication of units, interpret
                              non-multiplicative units as their *delta* counterparts.
+    :autoconvert_offset_to_baseunit: If True converts offset units in quantites are
+                                     converted to their base units in multiplicative
+                                     context. If False no conversion happens.
     :param on_redefinition: action to take in case a unit is redefined.
                             'warn', 'raise', 'ignore'
     :type on_redefintion: str
     """
 
-    def __init__(self, filename='', force_ndarray=False, default_to_delta=True, on_redefinition='warn'):
+    def __init__(self, filename='', force_ndarray=False, default_as_delta=True,
+                 autoconvert_offset_to_baseunit=False,
+                 on_redefinition='warn'):
         self.Quantity = build_quantity_class(self, force_ndarray)
         self.Measurement = build_measurement_class(self, force_ndarray)
 
@@ -491,9 +509,16 @@
         #: Maps dimensionality (_freeze(UnitsContainer)) to Units (_freeze(UnitsContainer))
         self._dimensionality_cache = TransformDict(_freeze)
 
+        #: Cache the unit name associated to user input. ('mV' -> 'millivolt')
+        self._parse_unit_cache = dict()
+
         #: When performing a multiplication of units, interpret
         #: non-multiplicative units as their *delta* counterparts.
-        self.default_to_delta = default_to_delta
+        self.default_as_delta = default_as_delta
+
+        # Determines if quantities with offset units are converted to their
+        # base units on multiplication and division.
+        self.autoconvert_offset_to_baseunit = autoconvert_offset_to_baseunit
 
         if filename == '':
             self.load_definitions('default_en.txt', True)
@@ -504,6 +529,9 @@
 
         self._build_cache()
 
+    def __name__(self):
+        return 'UnitRegistry'
+
     def __getattr__(self, item):
         return self.Quantity(1, item)
 
@@ -697,7 +725,8 @@
 
             _adder(alias, definition)
 
-        if isinstance(definition.converter, OffsetConverter):
+        # define additional "delta_" units for units with an offset
+        if getattr(definition.converter, "offset", 0.0) != 0.0:
             d_name = 'delta_' + definition.name
             if definition.symbol:
                 d_symbol = 'Δ' + definition.symbol
@@ -710,7 +739,7 @@
                     return '[delta_' + _name[1:]
                 return 'delta_' + _name
 
-            d_reference = UnitsContainer(dict((prep(ref), value)
+            d_reference = UnitsContainer(dict((ref, value)
                                          for ref, value in definition.reference.items()))
 
             self.define(UnitDefinition(d_name, d_symbol, d_aliases,
@@ -818,7 +847,7 @@
             return ''
 
         try:
-            return self._units[name_or_alias].name
+            return self._units[name_or_alias]._name
         except KeyError:
             pass
 
@@ -857,15 +886,17 @@
 
         return self._prefixes[prefix].symbol + self._units[unit_name].symbol
 
+    def _get_symbol(self, name):
+        return self._units[name].symbol
+
     def get_dimensionality(self, input_units):
         """Convert unit or dict of units or dimensions to a dict of base dimensions
 
         :param input_units:
         :return: dimensionality
         """
-        dims = UnitsContainer()
         if not input_units:
-            return dims
+            return UnitsContainer()
 
         if isinstance(input_units, string_types):
             input_units = ParserHelper.from_string(input_units)
@@ -873,24 +904,31 @@
         if input_units in self._dimensionality_cache:
             return copy.copy(self._dimensionality_cache[input_units])
 
-        for key, value in input_units.items():
+        accumulator = defaultdict(float)
+        self._get_dimensionality_recurse(input_units, 1.0, accumulator)
+
+        dims = UnitsContainer(dict((k, v) for k, v in accumulator.items() if v != 0.))
+
+        if '[]' in dims:
+            del dims['[]']
+
+        self._dimensionality_cache[input_units] = copy.copy(dims)
+
+        return dims
+
+    def _get_dimensionality_recurse(self, ref, exp, accumulator):
+        for key in ref:
+            exp2 = exp*ref[key]
             if _is_dim(key):
                 reg = self._dimensions[key]
                 if reg.is_base:
-                    dims.add(key, value)
-                else:
-                    dims *= self.get_dimensionality(reg.reference) ** value
+                    accumulator[key] += exp2
+                elif reg.reference is not None:
+                    self._get_dimensionality_recurse(reg.reference, exp2, accumulator)
             else:
                 reg = self._units[self.get_name(key)]
-                if reg.is_base:
-                    dims *= reg.reference ** value
-                else:
-                    dims *= self.get_dimensionality(reg.reference) ** value
-
-        if '[]' in dims:
-            del dims['[]']
-
-        return dims
+                if reg.reference is not None:
+                    self._get_dimensionality_recurse(reg.reference, exp2, accumulator)
 
     def get_base_units(self, input_units, check_nonmult=True):
         """Convert unit or dict of units to the base units.
@@ -914,27 +952,32 @@
         if check_nonmult and input_units in self._base_units_cache:
             return copy.deepcopy(self._base_units_cache[input_units])
 
-        factor = 1.
-        units = UnitsContainer()
-        for key, value in input_units.items():
-            key = self.get_name(key)
-            reg = self._units[key]
-            if reg.is_base:
-                units.add(key, value)
-            else:
-                fac, uni = self.get_base_units(reg.reference, check_nonmult=False)
-                if factor is not None:
-                    factor *= (reg.converter.scale * fac) ** value
-                units *= uni ** value
+        accumulators = [1., defaultdict(float)]
+        self._get_base_units(input_units, 1.0, accumulators)
+
+        factor = accumulators[0]
+        units = UnitsContainer(dict((k, v) for k, v in accumulators[1].items() if v != 0.))
 
         # Check if any of the final units is non multiplicative and return None instead.
         if check_nonmult:
             for unit in units.keys():
-                if not isinstance(self._units[unit].converter, ScaleConverter):
+                if not self._units[unit].converter.is_multiplicative:
                     return None, units
 
         return factor, units
 
+    def _get_base_units(self, ref, exp, accumulators):
+        for key in ref:
+            exp2 = exp*ref[key]
+            key = self.get_name(key)
+            reg = self._units[key]
+            if reg.is_base:
+                accumulators[1][key] += exp2
+            else:
+                accumulators[0] *= reg._converter.scale ** exp2
+                if reg.reference is not None:
+                    self._get_base_units(reg.reference, exp2, accumulators)
+
     def get_compatible_units(self, input_units):
         if not input_units:
             return 1., UnitsContainer()
@@ -967,9 +1010,9 @@
         :return: converted value
         """
         if isinstance(src, string_types):
-            src = ParserHelper.from_string(src)
+            src = self.parse_units(src)
         if isinstance(dst, string_types):
-            dst = ParserHelper.from_string(dst)
+            dst = self.parse_units(dst)
         if src == dst:
             return value
 
@@ -997,36 +1040,59 @@
         if src_dim != dst_dim:
             raise DimensionalityError(src, dst, src_dim, dst_dim)
 
-        if len(src) == 1:
-            # If the source has a single element, it might be a non-multiplicative unit
-            # and therefore it is treated differently.
-            src_unit, src_value = list(src.items())[0]
-            src_unit = self._units[self.get_name(src_unit)]
-
-            # We only continue if is a ScaleConverter,
-            # if not just exit to use the standard src / dst.
-            # TODO: This will fail and should not degK * meter / nanometer -> degC
-            if not isinstance(src_unit.converter, ScaleConverter):
-
-                if len(dst) > 1:
-                    # If the destination has more than one element,
-                    # then the conversion is not possible.
-                    # TODO: This will fail and should not degC -> degK * meter / nanometer
-                    raise DimensionalityError(src, dst, src_dim, dst_dim)
-
-                dst_unit, dst_value = list(dst.items())[0]
-                dst_unit = self._units[self.get_name(dst_unit)]
-                if not type(src_unit.converter) is type(dst_unit.converter):
-                    raise DimensionalityError(src, dst, src_dim, dst_dim)
-
-                return dst_unit.converter.from_reference(src_unit.converter.to_reference(value, inplace), inplace)
-
+        # Conversion needs to consider if non-multiplicative (AKA offset
+        # units) are involved. Conversion is only possible if src and dst
+        # have at most one offset unit per dimension.
+        src_offset_units = [(u, e) for u, e in src.items()
+                            if not self._units[u].is_multiplicative]
+        dst_offset_units = [(u, e) for u, e in dst.items()
+                            if not self._units[u].is_multiplicative]
+
+        # For offset units we need to check if the conversion is allowed.
+        if src_offset_units or dst_offset_units:
+
+            # Validate that not more than one offset unit is present
+            if len(src_offset_units) > 1 or len(dst_offset_units) > 1:
+                raise DimensionalityError(
+                    src, dst, src_dim, dst_dim,
+                    extra_msg=' - more than one offset unit.')
+
+            # validate that offset unit is not used in multiplicative context
+            if ((len(src_offset_units) == 1 and len(src) > 1)
+                    or (len(dst_offset_units) == 1 and len(dst) > 1)
+                    and not self.autoconvert_offset_to_baseunit):
+                raise DimensionalityError(
+                    src, dst, src_dim, dst_dim,
+                    extra_msg=' - offset unit used in multiplicative context.')
+
+            # Validate that order of offset unit is exactly one.
+            if src_offset_units:
+                if src_offset_units[0][1] != 1:
+                    raise DimensionalityError(
+                        src, dst, src_dim, dst_dim,
+                        extra_msg=' - offset units in higher order.')
+            else:
+                if dst_offset_units[0][1] != 1:
+                    raise DimensionalityError(
+                        src, dst, src_dim, dst_dim,
+                        extra_msg=' - offset units in higher order.')
+
+        # Here we convert only the offset quantities. Any remaining scaled
+        # quantities will be converted later.
+
+        # clean src from offset units by converting to reference
+        for u, e in src_offset_units:
+            value = self._units[u].converter.to_reference(value, inplace)
+            src.pop(u)
+
+        # clean dst units from offset units
+        for u, e in dst_offset_units:
+            dst.pop(u)
+
+        # Here src and dst have only multiplicative units left. Thus we can
+        # convert with a factor.
         factor, units = self.get_base_units(src / dst)
 
-        if factor is None:
-            raise DimensionalityError(src, dst, src_dim, dst_dim,
-                                      'Non-multiplicative unit found.')
-
         # factor is type float and if our magnitude is type Decimal then
         # must first convert to Decimal before we can '*' the values
         if isinstance(value, Decimal):
@@ -1037,6 +1103,16 @@
         else:
             value = value * factor
 
+        # Finally convert to offset units specified in destination
+        for u, e in dst_offset_units:
+            value = self._units[u].converter.from_reference(value, inplace)
+            # add back offset units to dst
+            dst[u] = e
+
+        # restore offset conversion of src units
+        for u, e in src_offset_units:
+            src[u] = e
+
         return value
 
     def pi_theorem(self, quantities):
@@ -1069,9 +1145,10 @@
         """Parse a unit to identify prefix, unit name and suffix
         by walking the list of prefix and suffix.
         """
-
-        for suffix, prefix in itertools.product(self._suffixes.keys(), self._prefixes.keys()):
-            if unit_name.startswith(prefix) and unit_name.endswith(suffix):
+        stw = unit_name.startswith
+        edw = unit_name.endswith
+        for suffix, prefix in itertools.product(self._suffixes, self._prefixes):
+            if stw(prefix) and edw(suffix):
                 name = unit_name[len(prefix):]
                 if suffix:
                     name = name[:-len(suffix)]
@@ -1079,30 +1156,33 @@
                         continue
                 if case_sensitive:
                     if name in self._units:
-                        yield (self._prefixes[prefix].name,
-                               self._units[name].name,
+                        yield (self._prefixes[prefix]._name,
+                               self._units[name]._name,
                                self._suffixes[suffix])
                 else:
                     for real_name in self._units_casei.get(name.lower(), ()):
-                        yield (self._prefixes[prefix].name,
-                               self._units[real_name].name,
+                        yield (self._prefixes[prefix]._name,
+                               self._units[real_name]._name,
                                self._suffixes[suffix])
 
-    def parse_units(self, input_string, to_delta=None):
+    def parse_units(self, input_string, as_delta=None):
         """Parse a units expression and returns a UnitContainer with
         the canonical names.
 
         The expression can only contain products, ratios and powers of units.
 
-        :param to_delta: if the expression has multiple units, the parser will
+        :param as_delta: if the expression has multiple units, the parser will
                          interpret non multiplicative units as their `delta_` counterparts.
 
         :raises:
             :class:`pint.UndefinedUnitError` if a unit is not in the registry
             :class:`ValueError` if the expression is invalid.
         """
-        if to_delta is None:
-            to_delta = self.default_to_delta
+        if input_string in self._parse_unit_cache:
+            return self._parse_unit_cache[input_string]
+
+        if as_delta is None:
+            as_delta = self.default_as_delta
 
         if not input_string:
             return UnitsContainer()
@@ -1113,16 +1193,19 @@
 
         ret = UnitsContainer()
         many = len(units) > 1
-        for name, value in units.items():
+        for name in units:
             cname = self.get_name(name)
+            value = units[name]
             if not cname:
                 continue
-            if to_delta and (many or (not many and abs(value) != 1)):
+            if as_delta and (many or (not many and value != 1)):
                 definition = self._units[cname]
                 if not definition.is_multiplicative:
                     cname = 'delta_' + cname
             ret[cname] = value
 
+        self._parse_unit_cache[input_string] = ret
+
         return ret
 
     def parse_expression(self, input_string, case_sensitive=True, **values):
@@ -1141,7 +1224,7 @@
         unknown = set()
         for toknum, tokval, _, _, _ in gen:
             if toknum == NAME:
-                # TODO: Integrate math better, Replace eval
+                # TODO: Integrate math better, Replace eval, make as_delta-aware
                 if tokval == 'pi' or tokval in values:
                     result.append((toknum, tokval))
                     continue
 
=== modified file 'setup.cfg'
--- setup.cfg	2014-09-05 23:26:05 +0000
+++ setup.cfg	2015-01-07 15:51:38 +0000
@@ -1,7 +1,13 @@
 [check-manifest]
-ignore =
-    .travis.yml
-    tox.ini
+ignore = 
+	.travis.yml
+	tox.ini
 
 [bdist_wheel]
 universal = 1
+
+[egg_info]
+tag_build = 
+tag_date = 0
+tag_svn_revision = 0
+
 
=== modified file 'setup.py'
--- setup.py	2014-09-05 23:26:05 +0000
+++ setup.py	2015-01-07 15:51:38 +0000
@@ -29,7 +29,7 @@
 
 setup(
     name='Pint',
-    version='0.5.2',
+    version='0.6',
     description='Physical quantities module',
     long_description=long_description,
     keywords='physical quantities unit conversion science',
 
=== removed file 'tox.ini'
--- tox.ini	2014-09-05 23:26:05 +0000
+++ tox.ini	1970-01-01 00:00:00 +0000
@@ -1,77 +0,0 @@
-[tox]
-envlist = py26,py27,py32,py33,numpy26,numpy27,numpy32,numpy33,
-          py26u,py27u,py32u,py33u,numpy26u,numpy27u,numpy32u,numpy33u
-
-[testenv]
-deps = coverage
-commands = coverage run -p --source=pint setup.py test
-
-setenv=
-    COVERAGE_FILE=.coverage.{envname}
-
-
-[testenv:py26]
-deps = unittest2
-       coverage
-
-[testenv:numpy26]
-deps = numpy
-       unittest2
-       coverage
-
-[testenv:numpy27]
-basepython=python2.7
-deps = numpy
-       coverage
-
-[testenv:numpy32]
-basepython=python3.2
-deps = numpy
-       coverage
-
-[testenv:numpy33]
-basepython=python3.3
-deps = numpy
-       coverage
-
-
-[testenv:py26u]
-deps = unittest2
-       uncertainties
-       coverage
-
-[testenv:py27u]
-deps = uncertainties
-       coverage
-
-[testenv:py32u]
-deps = uncertainties
-       coverage
-
-[testenv:py33u]
-deps = uncertainties
-       coverage
-
-[testenv:numpy26u]
-deps = numpy
-       unittest2
-       uncertainties
-       coverage
-
-[testenv:numpy27u]
-basepython=python2.7
-deps = numpy
-       uncertainties
-       coverage
-
-[testenv:numpy32u]
-basepython=python3.2
-deps = numpy
-       uncertainties
-       coverage
-
-[testenv:numpy33u]
-basepython=python3.3
-deps = numpy
-       uncertainties
-       coverage