Comment 19 for bug 882036

Some comparisons:

def r1(f, p=0):
    return round(f + cmp(f, 0) * pow(2, -52), p)

def r2(f, p=0):
    return round(f + cmp(f, 0.0) * (.1 / pow(10, p+2)), p)

for s in [-1, 1]:
    for f in [.674, .675, .676]:
        for p in [0.0, 1.0, 2.0, 3.0]:
            g = s*(f+p)
            print g, round(g,2), r1(g,2), r2(g,2)

-0.674 -0.67 -0.67 -0.67
-1.674 -1.67 -1.67 -1.67
-2.674 -2.67 -2.67 -2.67
-3.674 -3.67 -3.67 -3.67
-0.675 -0.68 -0.68 -0.68
-1.675 -1.68 -1.68 -1.68
-2.675 -2.67 -2.67 -2.68
-3.675 -3.67 -3.67 -3.68
-0.676 -0.68 -0.68 -0.68
-1.676 -1.68 -1.68 -1.68
-2.676 -2.68 -2.68 -2.68
-3.676 -3.68 -3.68 -3.68
0.674 0.67 0.67 0.67
1.674 1.67 1.67 1.67
2.674 2.67 2.67 2.67
3.674 3.67 3.67 3.67
0.675 0.68 0.68 0.68
1.675 1.68 1.68 1.68
2.675 2.67 2.67 2.68
3.675 3.67 3.67 3.68
0.676 0.68 0.68 0.68
1.676 1.68 1.68 1.68
2.676 2.68 2.68 2.68
3.676 3.68 3.68 3.68