isinf

isinf

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Tests whether a given floating point value is an infinity

 #include <math.h> int isinf ( float x  ); int isinf ( double x  ); int isinf ( long double x  ); 

The macro isinf( ) yields a nonzero value (that is, TRue) if its argument is a positive or negative infinity. Otherwise, isinf( ) yields 0. The argument must be a real floating-point type. The rule that floating-point types are promoted to at least double precision for mathematical calculations does not apply here; the argument's properties are determined based on its representation in its actual semantic type.

Example

This function takes a short cut if it encounters an infinite addend:

 double vsum( int n, va_list argptr ) {   double sum = 0.0, next = 0.0;   va_start( argptr, n );   for ( int i = 0; i < n; i ++ )   {     next = va_arg( argptr, double );     if ( isinf( next ) )       return next;     sum += next;   }   va_end( argptr );   return sum; } 

See Also

fpclassify( ), isfinite( ), isnan( ), isnormal( ), signbit( )