[Chicken-users] Re: IEEE float arithmetic

[Abdulaziz Ghuloum]

John Cowan wrote:

> Here are some handy C routines for detecting infs and nans that I worked
> out with Albert Gräf (the Q author):
>
> int isnan(double f) {
>         return !(f == f);
>         }
>
> int isinf(double f) {
>         return f == f + 1.0;
>         }
>
> The first one works because any comparison involving a NaN is always
> false.  In the second one, obviously no finite argument can return
> true, and although NaN + 1.0 gives NaN, it will still not compare equal
> to itself!

The second test is obviously bogus since f==f+1.0 for large values of f.
(try 1e16)

Aziz,,,