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_isnan, _isnanl

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.

Portability

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

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