C++ Function Template

Templates are powerful features of C++ which allows us to write generic programs.

We can create a single function to work with different data types by using a template.

Defining a Function Template

A function template starts with the keyword template followed by template parameter(s) inside <> which is followed by the function definition.

template <typename T>
T functionName(T parameter1, T parameter2, ...) {
    // code
}

In the above code, T is a template argument that accepts different data types (int, float, etc.), and typename is a keyword.

When an argument of a data type is passed to functionName(), the compiler generates a new version of functionName() for the given data type.

Calling a Function Template

Once we've declared and defined a function template, we can call it in other functions or templates (such as the main() function) with the following syntax

functionName<dataType>(parameter1, parameter2,...);

For example, let us consider a template that adds two numbers:

template <typename T>
T add(T num1, T num2) {
   return (num1 + num2);
}

We can then call it in the main() function to add int and double numbers.

int main() {

    int result1;
    double result2;
    // calling with int parameters
    result1 = add<int>(2, 3);
    cout << result1 << endl;

    // calling with double parameters
    result2 = add<double>(2.2, 3.3);
    cout << result2 << endl;

    return 0;
}    

Example: Adding Two Numbers Using Function Templates

#include <iostream>
using namespace std;

template <typename T>
T add(T num1, T num2) {
    return (num1 + num2);
}

int main() {
    int result1;
    double result2;
    // calling with int parameters
    result1 = add<int>(2, 3);
    cout << "2 + 3 = " << result1 << endl;

    // calling with double parameters
    result2 = add<double>(2.2, 3.3);
    cout << "2.2 + 3.3 = " << result2 << endl;

    return 0;
}

Output

2 + 3 = 5
2.2 + 3.3 = 5.5