check if floating point variable has 'normal' values

Question

how can i check if a floating point value is a normal number and does not have any crude states (+-inf, ind, nan, qnan, denormal ...).

Checking for identity with it self seems to work for nan, but the other states?

Sorry - i forgot to mention that I am tied to an C90 Compiler ;(

Answer 1

You can use isnormal macro:

#include <math.h>
int isnormal(real-floating x);

There are also isfinite, isinf and isnan macros.