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copysign, copysignf, copysignl

From cppreference.com
< c‎ | numeric‎ | math
 
 
 
Common mathematical functions
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Exponential functions
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Nearest integer floating point operations
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Floating point manipulation functions
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copysign
(C99)
Classification
(C99)
(C99)
(C99)
Macro constants
 
Defined in header <math.h>
float       copysignf( float x, float y );
(1) (since C99)
double      copysign( double x, double y );
(2) (since C99)
long double copysignl( long double x, long double y );
(3) (since C99)
Defined in header <tgmath.h>
#define copysign(from, to)
(7) (since C99)
1-3) Composes a floating point value with the magnitude of x and the sign of y.
4) Type-generic macro: If any argument has type long double, copysignl is called. Otherwise, if any argument has integer type or has type double, copysign is called. Otherwise, copysignf is called.

Contents

[edit] Parameters

x, y - floating point values

[edit] Return value

If no errors occur, the floating point value with the magnitude of x and the sign of y is returned.

If x is NaN, then NaN with the sign of y is returned.

If y is -0, the result is only negative if the implementation supports the signed zero consistently in arithmetic operations.

[edit] Error handling

This function is not subject to any errors specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

[edit] Notes

copysign is the only portable way to manipulate the sign of a NaN value (to examine the sign of a NaN, signbit may also be used).

[edit] Example

#include <stdio.h>
#include <math.h>
 
int main(void)
{
    printf("copysign(1.0,+2.0)      = %+.1f\n", copysign(1.0,+2.0));
    printf("copysign(1.0,-2.0)      = %+.1f\n", copysign(1.0,-2.0));
    printf("copysign(INFINITY,-2.0) = %f\n",    copysign(INFINITY,-2.0));
    printf("copysign(NAN,-2.0)      = %f\n",    copysign(NAN,-2.0));
}

Possible output:

copysign(1.0,+2.0)      = +1.0
copysign(1.0,-2.0)      = -1.0
copysign(INFINITY,-2.0) = -inf
copysign(NAN,-2.0)      = -nan

[edit] See also

(C99)(C99)
computes absolute value of a floating-point value (|x|)
(function) [edit]
checks if the given number is negative
(function) [edit]
C++ documentation for copysign