Function Templates

Like class templates, we can also define function templates that could be used to create a family of functions with different argument types. The general format of a function template is as follows:

template <class T> return-type function-name( argument of type T ) { // body of function with Type T }

The function template syntax is similar to that of the class template except that we are defining functions instead of classes. We must use the template parameter T as and when necessary in the function body and in its argument list.

The following example declares a swap() function template that will swap two values of a given type of data.

template <class T> void swap(T &x, T &y ) {      T temp = x ;      x = y ;      y = temp ; }

This essentially declares a set of overloaded functions, one for each type of data. We can invoke the swap() function like any ordinary function.

Example:

#include<iostream.h> template<class T> void swap( T &x, T &y ) {      T temp = x;      x = y;      y = temp; } void fun(int m, int n, float a, float b) {      cout<<"n m and n before swap : "<<m<<" " <<n;      swap(m, n);      cout<<"n m and n after swap : "<<m<<" " <<n;      cout<<"n a and b before swap : "<<a<<" " <<b;      swap(a, b);      cout<<"n a and b after swap : "<<a<<" " <<b; } void main() {      fun(100, 200, 11.22, 33.44); }

Output:

Function Templates with Multiple Parameters

We can use more than one generic data type in the template statement, using a comma- separated list as shown below:

template < class T1, class T2 > return-type function-name(argument of types T1, T2,…) { // body of the function }

Example: