fpclassify

fpclassify

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Obtains a classification of a real floating-point number

 #include <math.h> int fpclassify ( x  ); 

The fpclassify( ) macro determines whether its argument is a normal floating-point number, or one of several special categories of values, including NaN (not a number), infinity, subnormal floating-point values, zero, and possibly other implementation-specific categories.

To determine what category the argument belongs to, compare the return value of fpclassify( ) with the values of the following number classification macros, defined in math.h:

FP_INFINITE

FP_NAN

FP_NORMAL

FP_SUBNORMAL

FP_ZERO

These five macros expand to distinct integer values.

Example

 double minimum( double a, double b ) {   register int aclass = fpclassify( a );   register int bclass = fpclassify( b );   if ( aclass == FP_NAN || bclass == FP_NAN )     return NAN;   if ( aclass == FP_INFINITE )        // -Inf is less than anything;     return ( signbit( a ) ? a : b );  // +inf is greater than anything.   if ( bclass == FP_INFINITE )     return ( signbit( b ) ? b : a );   return ( a < b ? a : b ); } 

See Also

isfinite( ), isinf( ), isnan( ), isnormal( ), signbit( )