copysign(), copysignf(), copysignl()

Copy the sign bit from one number to another

Synopsis:

#include <math.h>

double copysign ( double x,
                  double y);

float copysignf ( float x,
                  float y );

long double copysignl ( long double x,
                        long double y);

Arguments:

x: The number to use the magnitude of.
y: The number to use the sign of.

Library:

libm

Use the -l m option to qcc to link against this library.

Description:

The copysign(), copysignf(), and copysignl() functions return the magnitude of x with the sign bit of y.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

Call feclearexcept(FE_ALL_EXCEPT) before calling copysign(), copysignf(), or copysignl().
On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

Returns:

The magnitude of x with the sign bit of y.

If `x` is:	These functions return:	Errors:
NaN	NaN, with the same sign as `y`	—

Examples:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char** argv) 
{
   double a, b, c;

   a = 27.0;
   b = -5;
   c = copysign(a, b);
   printf("The magnitude of %f and sign of %f gives %f\n",
          a, b, c);

   return(EXIT_SUCCESS);
}

produces the output:

The magnitude of 27.000000 and sign of -5.000000 gives -27.000000

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	No
Thread	Yes