template

cppreference.com > C/C++ Keywords > template

Syntax:

  template <class data-type> return-type name( parameter-list ) {
  statement-list;
  }

Templates are used to create generic functions and can operate on data without knowing the nature of that data. They accomplish this by using a placeholder data-type for which many other data types can be substituted.

For example, the following code uses a template to define a generic swap function that can swap two variables of any type:

   template<class X> void genericSwap( X &a, X &b ) {
     X tmp;		

     tmp = a;
     a = b;
     b = tmp;
   }
   int main(void) {
     ...
     int num1 = 5;
     int num2 = 21;
     cout << "Before, num1 is " << num1 << " and num2 is " << num2 << endl;
     genericSwap( num1, num2 );
     cout << "After, num1 is " << num1 << " and num2 is " << num2 << endl;
     char c1 = 'a';
     char c2 = 'z';
     cout << "Before, c1 is " << c1 << " and c2 is " << c2 << endl;
     genericSwap( c1, c2 );
     cout << "After, c1 is " << c1 << " and c2 is " << c2 << endl;
     ...
     return( 0 );
   }