Synopsis

Tests whether a given floating point value is an infinity

#include <math.h>
intisinf( float x );
int isinf( double x );
int isinf( long double x );

The macro isinf() yields a nonzero value (that is, true) if its argument is a positive or negative infinity. Otherwise, isinf() yields 0. The argument must be a real floating-point type. The rule that floating-point types are promoted to at least double precision for mathematical calculations does not apply here; the argument's properties are determined based on its representation in its actual semantic type.