function
<cmath> <ctgmath>

copysign

     double copysign  (double x     , double y);
      float copysignf (float x      , float y);
long double copysignl (long double x, long double y);

     double copysign (double x     , double y);
      float copysign (float x      , float y);
long double copysign (long double x, long double y);
     double copysign (Type1 x      , Type2 y);       // additional overloads
Copy sign
Returns a value with the magnitude of x and the sign of y.

Header <tgmath.h> provides a type-generic macro version of this function.
Additional overloads are provided in this header (<cmath>) for other combinations of arithmetic types (Type1 and Type2): These overloads effectively cast its arguments to double before calculations, except if at least one of the arguments is of type long double (in which case both are casted to long double instead).

Parameters

x
Value with the magnitude of the resulting value.
y
Value with the sign of the resulting value.

Return Value

The value with a magnitude of x and the sign of y.

Example

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/* copysign example */
#include <stdio.h>      /* printf */
#include <math.h>       /* copysign */

int main ()
{
  printf ("copysign ( 10.0,-1.0) = %f\n", copysign( 10.0,-1.0));
  printf ("copysign (-10.0,-1.0) = %f\n", copysign(-10.0,-1.0));
  printf ("copysign (-10.0, 1.0) = %f\n", copysign(-10.0, 1.0));

  return 0;
}


Output:

copysign ( 10.0,-1.0) = -10.0
copysign (-10.0,-1.0) = -10.0
copysign (-10.0, 1.0) = 10.0

See also

fabs
Compute absolute value (function )

C++