Math Library (libm, -lm)

SYNOPSIS

     #include <math.h>

     int
     fpclassify(real-floating x);

     int
     isfinite(real-floating x);

     int
     isinf(real-floating x);

     int
     isnan(real-floating x);

     int
     isnormal(real-floating x);

DESCRIPTION

     The fpclassify() macro takes an argument of x and returns one of the fol-
     lowing manifest constants.

     FP_INFINITE   Indicates that x is an infinite number.

     FP_NAN        Indicates that x is not a number (NaN).

     FP_NORMAL     Indicates that x is a normalized number.

     FP_SUBNORMAL  Indicates that x is a denormalized number.

     FP_ZERO       Indicates that x is zero (0 or -0).

     The isfinite() macro returns a non-zero value if and only if its argument
     has a finite (zero, subnormal, or normal) value.  The isinf(), isnan(),
     and isnormal() macros return non-zero if and only if x is an infinity,
     NaN, or a non-zero normalized number, respectively.

     The symbol isnanf() is provided as an alias to isnan() for compatibility,
     and its use is deprecated.

SEE ALSO

     isgreater(3), math(3), signbit(3)

STANDARDS

     The fpclassify(), isfinite(), isinf(), isnan(), and isnormal() macros
     conform to ISO/IEC 9899:1999 (``ISO C99'').

HISTORY

     3BSD introduced isinf() and isnan() functions, which accepted double
     arguments; these have been superseded by the macros described above.