_isnan, _isnanl

Remonter à float.h - Index

Header File

float.h

Category

Classification Routines, Math Routines

Prototype

int _isnan(double d);

int _isnanl(long double ld);

Description

Tests whether a given double-precision floating-point value d is a NaN.

_isnanl is the long double version; it takes a long double argument.

Return Value

Returns a nonzero value (TRUE) if the value passed in is a NaN; otherwise it returns 0 (FALSE). The non-zero return value corresponds to either _FPCLASS_SNAN, if the NaN is of the signaling type, or _FPCLASS_QNAN, if the NaN is of the quiet type. The values for _FPCLASS_SNAN and _FPCLASS_QNAN are in float.h.

Example

#include <math.h>
int print_double(double value)
{
  /* print "Infinite" if value is NaN */
  if (_isnan(value))
    printf("Infinite");
  else
    printf("%f", value);
}

Portability

	POSIX	Win32	ANSI C	ANSI C++
_isnan		+
_isnanl		+