On Mon, Sep 18, 2000 at 06:40:23PM +0200, Robert Hegemann wrote:
> Frank Klemm schrieb am Mon, 18 Sep 2000:
> > ::
> > :: 1) one type is long double, the other will be casted to long double
> > :: 2) one type is double, the other will be casted to double
> > :: 3) one type is float, the other will be casted to float
> > Fully wrong.
> > The rest I haven't checked.
> >
> > --
> > Mit freundlichen Grüßen
> > Frank Klemm
>
> You may like to look into Microsoft Developer Studio's help
> text, section "Usual Arithmetic Conversions", as you call
> this to be wrong too.
>
Microsoft's Developer Studio is fine, but far beyond being standard conform.
Gcc is a little bit better, especially with a lot of force-conformity
flags.
#include <stdio.h>
float x1 = 1.e30;
float x2 = 1.e31;
float x3 = 1.e32;
int main ( void )
{
float x4;
x4 = x1*x2*x3 / (x1*x2 + x2*x3 + x3*x1);
printf ( "%g\n", x4 );
return 0;
}
The code line x4=... is equivalent to
x4 = (float) ((double)x1*x2*x3 / ((double)x1*x2 + (double)x2*x3 + (double)x3*x1));
Note, that the optimizer of gcc-2.95 isn't standard conform.
One exception for implicit type conversations are functions calls of prototyped
functions (Note: Not in K&R2, but in ANSI C3.159-1989 and later).
--
Frank Klemm
PS: Nice try for MS VC++:
unsigned __int64 x = 123456789012345LL;
double y;
y = x;
--
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