# integers and floating points

**btanksley@hifn.com**
btanksley@hifn.com

*Wed, 27 Oct 1999 09:47:21 -0700*

>* From: Laurent Martelli [mailto:martelli@iie.cnam.fr]
*>* Subject: Re: integers and floating points
*
>* >>>>> "JS" == shapj <shapj@us.ibm.com> writes:
*
>* JS> Let's not be so open and high level that we allow ourselves to
*>* JS> ignore mathematical realities. Integers and floating point
*>* JS> numbers have deeply different mathematical properties, and in
*>* JS> the end a high-level system is no good unless it generates the
*>* JS> results the user wants to see.
*
>* Yes, but the set of integers is a subset of the reals, so they are not
*>* so different. That's why we exepect to be able to add an integer and a
*>* real.
*
Don't expect that anymore; it's wrong. The set of integers is not a subset
of the floats; there are integers which cannot be represented as floats.
(x+y)-x is not always equal to x+(y-x) in floating point math. It's always
true for integers.
>* Laurent Martelli
*
-Billy