# [PYTHON MATRIX-SIG] floating point equalities

**L. Larrabee Strow
**
strow@umbc.edu

*Tue, 23 Jan 1996 14:40:48 -0500*

>*In preparation for the 0.30 release (still on for Friday) I've been
*>*cleaning up the array math functions.
*>*
*>*I'm now working on improving the floating point equality operator. My
*>*understanding is that doing a == b is unreasonable for floating point
*>*numbers, and instead the test should be something like
*>*
*>*abs(a-b) < TOLERANCE*abs(a)
*>*
*>*Rather than have me try and rederive what this should look like from
*>*my vague memories of the IEEE floating point standard, I was wondering
*>*if anybody out there has a good chunk of code for doing this
*>*comparision?
*>*
*>*Thanks, Jim
*>*
*
Let the user decide how to compare for equality. We are used to avoiding
the a==b problem. It would probably be a mistake to "help" us too much,
since we might get lazy and make even more subtle mistakes.
--
L. Larrabee Strow E-mail: strow@umbc.edu
Department of Physics FAX : (410) 455-1072
University of Maryland Baltimore County Phone : (410) 455-2528
5401 Wilkens Avenue
Baltimore, MD 21228-5398
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