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Re: [vox-tech] c program in linux vs sgi
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Re: [vox-tech] c program in linux vs sgi



On Sat, 18 Nov 2000, Qinghua Zhong wrote:

> 2) if condition problem-->never happend in sgi machines again.
>    x is 0.55 (double variable)
>    y is 55 (int variable), z is 100 (int variable)
>    (x == (double) y / (double) z) returns false.
>    how come?

Rewrite the following:

   if(x == (double)y / (double)z)

to:

   if(fabs(x - (double)y / (double)z) < SMALL_AMT)

where SMALL_AMT is the smallest error you're willing to accept, such as
0.0000000000001 (or whatever).  Jeff's description of difference by small
amount in floating point numbers is the reason why you need to do this
with floating point (whether it be single or double) numbers.

-Mark

---
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.


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