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C++ Function Templates

You can create a function template by using the template keyword:

Syntax

template < typename T
>
return_type
function_name
( T parameter ) {
 // code
}

T is a placeholder for a data type (like int , float , etc.).
You can use any name instead of T , but T is common.

Example

template <typename T> T add(T a, T b) {
  return a + b;
}
int main() {
  cout << add<int>(5, 3) << "\n";
  cout << add<double>(2.5, 1.5) << "\n";
  return 0;
}

In the example above, add<int>(5, 3) tells the compiler to use int for T , while add<double>(2.5, 1.5) tells it to use double .

C++ Class Templates

You can also use templates to make classes that work with any data type:

Syntax

template < typename T
> class
ClassName {
 // members and methods using T
};

The example below defines a template class Box that can store and display a value of any data type, and then creates one box for an int and one for a string :

Example

template <typename T> class Box {
  public: T value;
  Box(T v) {
    value = v;
  }
void show() {
  cout << "Value: " << value << "\n";
}
};
int main() {
  Box<int> intBox(50);
  Box<string> strBox("Hello");
  intBox.show();
  strBox.show();
  return 0;
}

And this example defines a template class Pair that stores two values of different types and displays them, then creates one pair for a person's name and age, and another for an ID and score:

Example

template <typename T1, typename T2> class Pair {
  public: T1 first;
  T2 second;
  Pair(T1
  a, T2 b) {
    first = a;
    second = b;
  }
void display() {
  cout << "First: " << first << ", Second: " << second << "\n";
}
};
int main() {
  Pair<string, int> person("John", 30);
  Pair<int, double> score(51, 9.5);
  person.display();
  score.display();
  return 0;
}

C++ Function Templates

You can create a function template by using the template keyword:

Syntax

template < typename T
>
return_type
function_name
( T parameter ) {
 // code
}

T is a placeholder for a data type (like int , float , etc.).
You can use any name instead of T , but T is common.

Example

template <typename T> T add(T a, T b) {
  return a + b;
}
int main() {
  cout << add<int>(5, 3) << "\n";
  cout << add<double>(2.5, 1.5) << "\n";
  return 0;
}

In the example above, add<int>(5, 3) tells the compiler to use int for T , while add<double>(2.5, 1.5) tells it to use double .

C++ Class Templates

You can also use templates to make classes that work with any data type:

Syntax

template < typename T
> class
ClassName {
 // members and methods using T
};

The example below defines a template class Box that can store and display a value of any data type, and then creates one box for an int and one for a string :

Example

template <typename T> class Box {
  public: T value;
  Box(T v) {
    value = v;
  }
void show() {
  cout << "Value: " << value << "\n";
}
};
int main() {
  Box<int> intBox(50);
  Box<string> strBox("Hello");
  intBox.show();
  strBox.show();
  return 0;
}

And this example defines a template class Pair that stores two values of different types and displays them, then creates one pair for a person's name and age, and another for an ID and score:

Example

template <typename T1, typename T2> class Pair {
  public: T1 first;
  T2 second;
  Pair(T1
  a, T2 b) {
    first = a;
    second = b;
  }
void display() {
  cout << "First: " << first << ", Second: " << second << "\n";
}
};
int main() {
  Pair<string, int> person("John", 30);
  Pair<int, double> score(51, 9.5);
  person.display();
  score.display();
  return 0;
}

C++ Templates

C++ Function Templates

C++ Class Templates

Why Use Templates?

C++ Templates

C++ Function Templates

C++ Class Templates

Why Use Templates?