| 1 |
On Thursday 27 October 2005 13:52, Darren Dale wrote: |
| 2 |
> |
| 3 |
> Here is another test: |
| 4 |
> |
| 5 |
> #include <math.h> |
| 6 |
> #include <stdio.h> |
| 7 |
> |
| 8 |
> int main() { |
| 9 |
> printf("signbit(-1): %d\n", signbit(-1)); |
| 10 |
> printf("isnan(0.0/0): %d\n", isnan(0.0/0)); |
| 11 |
> printf("isinf(1.0/0): %d\n", isinf(1.0/0)); |
| 12 |
> return 0; |
| 13 |
> } |
| 14 |
> |
| 15 |
> which yields: |
| 16 |
> |
| 17 |
> signbit(-1): -2147483648 |
| 18 |
> isnan(0.0/0): 1 |
| 19 |
> isinf(1.0/0): 1 |
| 20 |
> |
| 21 |
> Do you know why signbit doesn't yield 1? |
| 22 |
|
| 23 |
The answer is in 'man signbit'. |
| 24 |
|
| 25 |
signbit is probably just ANDing your float value with 2^31=0x80000000 which |
| 26 |
reads -2147483648 if considered as a signed int (like in your printf). |
| 27 |
|
| 28 |
Miguel |
| 29 |
-- |
| 30 |
gentoo-science@g.o mailing list |
Archives