[Patches] [ python-Patches-1478364 ] Picky floats

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Patches item #1478364, was opened at 2006-04-28 07:33
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Category: Core (C code)
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Skip Montanaro (montanaro)
Assigned to: Nobody/Anonymous (nobody)
Summary: Picky floats

Initial Comment:
I came across a bug at work yesterday where I had
written:

    if not delta:
        return 0.0

where delta was a floating point number.  After a
series of calculations piling up round-off error it
took on a value on the order of 1e-8.  Not zero, but it
should have been.  The fix was easy enough:

    if abs(delta) < EPSILON:
        return 0.0

for a suitable value of EPSILON.

That got me to thinking...  I'm sure I have plenty of
other similar mistakes in my code.  (Never was much of
a numerical analysis guy...)  What if there was a
picky-float configure option that generated warnings if
you compared a float with either another float or an
int using "=="?  Does that make sense to try for
testing purposes?  The initial implementation seemed
straightforward enough, though I'm sure if this idea
merits any serious consideration it will need some more
work (at the least this behavior should probably be
user-enabled).


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