Monday, 20 April 2009

An example of using Typename with Templates

Typename is used with templates where the type is unknown. Use the keyword typename if you have a qualified name that refers to a type and depends on a template parameter. Only use the keyword typename in template declarations and definitions.


//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
//This program shows an how to use typename with templates
//Example from
//http://www.deitel.com/articles/cplusplus_tutorials/20060428/index.html
#include<iostream>

//using namespace std; //No need to use the whole namespace std
using std::cout;
using
std::endl;

// function template printArray definition
template<typename T>
void
printArray( const T *array, int count )
{

for
( int i = 0; i < count; i++ )
{

cout << array[ i ] << " ";
}

cout << endl;
}
// end function template printArray

int
main()
{

const
int ACOUNT = 5; // size of array a
const int BCOUNT = 7; // size of array b
const int CCOUNT = 6; // size of array c

int
a[ ACOUNT ] = { 1, 2, 3, 4, 5 };
double
b[ BCOUNT ] = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7 };
char
c[ CCOUNT ] = "HELLO"; // 6th position for null

cout << "Array a contains:" << endl;
// call integer function-template specialization
printArray( a, ACOUNT );

cout << "Array b contains:" << endl;
// call double function-template specialization
printArray( b, BCOUNT );

cout << "Array c contains:" << endl;
// call character function-template specialization
printArray( c, CCOUNT );

return
0;
}



Note in the above example you could have replaced 'typename' with 'class' and obtain the same results. Compare this with our basic template example discussed before.

The output of the program is as follows:

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