std::copysign

From Cppreference

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Defined in header <cmath>
float       copysign( float x, float y );	(1)	(since C++11)
double      copysign( double x, double y );	(2)	(since C++11)
long double copysign( long double x, long double y );	(3)	(since C++11)
Promoted    copysign( Arithmetic x, Arithmetic y );	(4)	(since C++11)

Composes a floating point value with the magnitude of x and the sign of y.

4) If any argument has integral type, it is cast to double. If any other argument is long double, then the return type is long double, otherwise it is double.

[edit] Parameters

x, y

-

floating point values

[edit] Return value

floating point value with the magnitude of x and the sign of y

[edit] See also

abs(float) fabs	absolute value of a floating point value (|x|) (function)
signbit (C++11)	checks if the given number is negative (function)