72c
Subj : Re: Serious Problem with precision or if statement
To   : borland.public.cpp.borlandcpp
From : "Sebastian Ledesma" <labo@solidyne1.com>
Date : Thu Aug 14 2003 12:51 pm

Hi:

Did you checked the 'FAST FLOATING POINT' option in
Options->Project->Compiler->Floating Point ?

Saludos
Sebastian

"Chris" <mudd1_wheels@hotmail.com> escribió en el mensaje
news:3f3a4f95$1@newsgroups.borland.com...
>
> Hi everyone.
> I am having a problem with the following program. It's very
> simple but the results are very unexpected (at least I think so).
>
> code
> -----------------------
> #include <stdio.h>
>
> int main() {
>
>   int Phase = 3;
>
>   if( Phase/3.0 == 1.0 )
>     printf("equal");
>   else
>     printf("not equal");
>
>   return 1;
> }
> -----------------------
>
> Now we would expect "equal" to be printed, but to my
> (everyone's) surprise, "not equal" is printed.
>
> An even more extraordinary thing occurs when tracing the program.
> The expression ( Phase/3.0 == 1.0 ) evaluates to TRUE. However,
> the else(FALSE) branch is taken printing "not equal"!
>
> I have tried several modifications to the if statement
> to no avail.
>
> if( (double)Phase/3 == 1.0 )
> if( Phase/3.0 == (double) 1 )
>
> It is worthwhile to note that
> if( Phase/3 == 1 ) does return the correct answer.
>
> Assigning the value (Phase/3.0) to an intermediate double x
> and then checking if( x == 1.0 ) also works.
>
> If anyone has time or wants some amusement, run my program.
> I am using Borland C++ 5.02 on an Intel Pentium III with Windows
> XP. I get the same results with a AMD Duron with Windows 98.
>
> Under LINUX compiled for i586, compiling and running my program
> with gcc returns "equal", the correct answer.
>
> Thanks. Please post your answers or results.

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