On Thursday 27 October 2005 13:52, Darren Dale wrote:
>
> Here is another test:
>
> #include <math.h>
> #include <stdio.h>
>
> int main() {
> printf("signbit(-1): %d\n", signbit(-1));
> printf("isnan(0.0/0): %d\n", isnan(0.0/0));
> printf("isinf(1.0/0): %d\n", isinf(1.0/0));
> return 0;
> }
>
> which yields:
>
> signbit(-1): -2147483648
> isnan(0.0/0): 1
> isinf(1.0/0): 1
>
> Do you know why signbit doesn't yield 1?
The answer is in 'man signbit'.
signbit is probably just ANDing your float value with 2^31=0x80000000 which
reads -2147483648 if considered as a signed int (like in your printf).
Miguel
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