isnan(S)                       6 January 1993                       isnan(S)


 Name

    isnan, isnand, isnanf - test for a floating point NaN (Not-A-Number)

 Syntax


    cc  . . .  -lm


    #include <nan.h>

    int isnan (x)
    double x;


    cc  . . .  -lc


    #include <ieeefp.h>

    int isnand (dsrc)
    double dsrc;

    int isnanf (fsrc)
    float fsrc;


 Description

    The isnand and isnanf functions return true (1) if the argument dsrc or
    fsrc is a NaN; otherwise they return false (0).

    Neither routine generates any exception, even for signaling NaNs.

    The routine isnand is implemented in libc, the Standard C Library.
    isnanf is implemented as a macro included in <ieeefp.h>.

    The isnan routine in libm calls the NaN macro defined in <nan.h>.

 See also

    fpgetround(S)

 Standards conformance

    isnan is conformant with:
    Intel386 Binary Compatibility Specification, Edition 2 (iBCSe2).