IsNan and IsInf Functions

[SMcNeill]

If one ever needs to determine if a calculation generates a Nan result or an INF result, they can always use the following little snippet of code:

Save as isnan.h:

Code: (Select All)

#include <stdio.h>
#include <math.h>
#include <float.h>
int IsNan (long double n);
int IsInf (long double n);
IsNan (long double n) { return -isnan(n); }
IsInf (long double n) { return -isinf(n); }

And the test code to check for NaN and Inf:

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DECLARE LIBRARY "isnan"

    FUNCTION IsNan% (BYVAL n AS _FLOAT)

    FUNCTION IsInf% (BYVAL n AS _FLOAT)

END DECLARE

PRINT IsNan(0 / 0), IsInf(0 / 0)

PRINT IsInf(1 / 0), IsInf(1 / 0)

PRINT IsInf(0 / 1), IsInf(0 / 1)

Notice the output is:
0 / 0 is NaN but is *not* INF.
1 / 0 is NaN and is also INF.
0 / 1 is neither NaN, nor is it INF.