Header File 

float.h 

Category 

Math Routines 

Prototype 

double _copysign(double da, double db); 

long double _copysignl(long double lda, long double ldb); 

Description 

Returns the double-precision floating point argument da, with the same sign as the double-precision floating-point argument db. 

_copysignl is the long double version; it takes a long double argument and returns a long double result. 

Return Value 

Returns the first value with the same magnitude and exponent, but with the sign of the second value. There is no error value returned. 

Portability