The **`copysign` function** takes in two arguments and returns a value with the magnitude of the first argument and the sign of the second argument.



To use the `copysign` function, the `cmath` header file needs to be included in the program:
```C++
#include <cmath>
```

# Parameters
The function takes in two parameters: 
1. The first parameter determines the magnitude of the return value. 
2. The second parameter determines the sign of the return value.

# Return value

The `copysign` function can have the return value of three types:
* float
* double
* long double

These types depend on the types of arguments the programmer gives to the functions.
> If any argument passed to the `copysign` function is `long double`, the return type is `long double`. If not, the return type is `double`. If both the arguments are of type `float`, the return type is also `float`.



# Example
1. The code below shows the execution of a `copysign` function when both the arguments are of the same type. The value returned in line 11 is also `double, which is the same as its arguments.

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

int main() {
  //both the arguments are of type double
  double x = 22;
  double y = - 3;
  // prints the return value to the standard output
  cout << "The returned value is  " << copysign(x, y) << endl;
  // the type of returned value is output d which means the returned value is of type double.
  cout << "The type of returned value is " << typeid(copysign(x, y)).name() << endl;
  
  return 0;
}

2. The code below shows the `copysign` function when the arguments are of different types:

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

int main()
{   // first argument of type int
    int x = 34;
    //second argument of type double
    double y = -54.3;
    // prints the return value to the standard output
    cout << "The returned value is  " << copysign(x, y) << endl;
    // the type of returned value is output d which means returned value is of type double.
    cout << "The type of returned value is " << typeid(copysign(x, y)).name() << endl;

    return 0;
}

How to use copysign() in C++

The copysign function in C++ returns a value with the magnitude of the first argument and the sign of the second.