SYNOPSIS
#include <math.h>
int fpclassify(x);
int isfinite(x);
int isnormal(x);
int isnan(x);
int isinf(x);
Compile with -std=c99; link with -lm.
DESCRIPTION
Floating point numbers can have special values, such as infinite or
NaN. With the macro fpclassify(x) you can find out what type x is. The
macro takes any floating-point expression as argument. The result
takes one of the following values:
FP_NAN x is "Not a Number".
FP_INFINITE
x is either plus or minus infinity.
FP_ZERO
x is zero.
FP_SUBNORMAL
x is too small to be represented in normalized format.
FP_NORMAL
if nothing of the above is correct that it must be a normal
floating-point number.
The other macros provide a short answer to some standard questions.
isfinite(x)
returns a non-zero value if
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
isnormal(x)
returns a non-zero value if (fpclassify(x) == FP_NORMAL)
isnan(x)
returns a non-zero value if (fpclassify(x) == FP_NAN)
isinf(x)
returns 1 if x is positive infinity, and -1 if x is negative
infinity.