The **`copysignf` function** returns the value formed by combining the `magnitude of the first parameter` and the `sign of the second parameter`.

The `copysignf` function is a variation of the `copysign` function. The`f` in the variation refers to the `float` datatype of the parameter and return value. 



# Library
The `copysignf` function can be accessed via the `math.h` library.
# Syntax
```c
float copysignf(float x, float y)
```
# Parameters
The `copysignf` function takes two parameters of the `float` datatype.
# Return value
If no errors occur, the `copysignf` function returns a value of `float` datatype. This value has the `magnitude of the first parameter` and the `sign of the second parameter`.

If the `first parameter` is `NaN` (not a number), then the return value is `NaN` with the sign of the `second parameter`.

If the `second parameter` is `-0`, a negative value is returned (if a signed zero is supported in arithmetic operations).

> The `copysignf` function provides a way to manipulate the sign of `NaN`.

# Code
The following code shows the return values associated to different kinds of parameters:






#include <stdio.h>
#include <math.h>
 
int main()
{
    printf("copysignf(10,+4.0)         = %f\n", copysignf(10,+4.0)); 
    printf("copysignf(20,-8.0)         = %f\n", copysignf(20,-8.0));
    printf("copysignf(INFINITY,-2.0)   = %f\n", copysignf(INFINITY,-2.0)); //%f is the string formatter for float numbers
    printf("copysignf(NAN,-3.0)        = %f\n", copysignf(NAN,-3.0));
}

What is copysignf in C?

The copysignf function combines the magnitude of the first float parameter with the sign of the second.