C++ copysign(x, y) - Returns Value of x and Sign of y

In this C++ tutorial, you will learn how to use copysign(x, y) function of cmath to get a new value with the magnitude of x and sign of y, with syntax and examples.

C copysign

C++ copysign(x, y) returns a new value with the magnitude of x and sign of y.

Syntax

The syntax of C++ copysign() is

copysign(x, y)

where

Parameter	Description
x	A double, float, long double, or integral type value.
y	A double, float, long double, or integral type value.

Returns

The return value depends on the type of value passed for parameters x and y. The return value of copysign() is

double if x and y are double.
float if x and y are float.
long double if x and y are long double.
Promoted to the higher of the given arguments for integral type arguments.

The synopsis of copysign() function is

double copysign(double x, double y);
float copysign(float x, float y);
long double copysign(long double x, long double y);
Promoted copysign(Type1 x, Type2 y); // for integral type argument values

copysign() is a function of cmath library. Include cmath library at the start of program, if using copysign() function.

Example

In this example, we read two values from user into x and y, and find the return value of copysign(x, y) function.

C++ Program

#include <iostream>
#include<cmath>
using namespace std;

int main() {
    double x, y, z;
    cout << "Enter x : ";
    cin >> x;
    cout << "Enter y : ";
    cin >> y;

    double result = copysign(x, y);
    cout << "copysign(x, y) : " << result << endl;
}

Output

Enter x : 5
Enter y : -2
copysign(x, y) : -5
Program ended with exit code: 0

x is positive and y is negative, hence result is negative.

Run#2

Enter x : -5
Enter y : -2
copysign(x, y) : -5
Program ended with exit code: 0

x is negative and y is negative, hence result is negative.

Run#3

Enter x : -5
Enter y : 2
copysign(x, y) : 5
Program ended with exit code: 0

x is negative and y is positive, hence result is positive.

Run#4

Enter x : 5
Enter y : 2
copysign(x, y) : 5
Program ended with exit code: 0

x is positive. and y is positive, hence result is positive.

Conclusion

In this C++ Tutorial, we learned the syntax of C++ copysign(), and how to use this function, with the help of examples.