In this C++ tutorial, you will learn how to compute the value of (x*y + z) using fma() function of cmath, with syntax and examples.

C fma

C++ fma(x, y, z) computes and returns the value of (x*y + z).

Syntax

The syntax of C++ fma() is 

fma(x, y, z)

where

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

Returns

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

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

The synopsis of fma() function is

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

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

Example

In this example, we read three values from user into x, y and z, and find the value of x*y+z using fma() 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;
    cout << "Enter z : ";
    cin >> z;

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

Output

Enter x : 5
Enter y : 2
Enter z : 3
fma(x, y, z) : 13
Program ended with exit code: 0

Run#2

If any of the arguments is inf, then fma() returns inf.

Enter x : inf
Enter y : 10
Enter z : 2
fma(x, y, z) : inf
Program ended with exit code: 0

Run#3

If any of the arguments is -inf, then fma() returns -inf.

Enter x : -inf
Enter y : 2
Enter z : 3
fma(x, y, z) : -inf
Program ended with exit code: 0

Conclusion

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