template
Syntax:
template <class data-type> return-type name( parameter-list ) { statement-list; }
Templates are used to create generic functions and generic classes 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. Example code: 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 ); }
The next template is used to descibe a generic class:
#include <cassert> const unsigned int maxSize = 20; template<class T> class simpleStack { public: simpleStack(): amount(0) {} bool empty() const { return amount == 0; } bool full() const { return amount == maxSize; } unsigned int size() const { return amount; } void clear() { amount = 0; } const T& top() const; void pop(); void push( const T &x); private: unsigned int amount; T array[ maxSize ]; }; template<class T> const T& simpleStack<T>::top() const { assert( !empty() ); return array[ amount - 1 ]; } template<typename T> /*it's allowed and equal to replace class with typename*/ void simpleStack<T>::pop() { assert( !empty() ); --amount; } template<typename T> void simpleStack<T>::push(const T &x) { assert( !full() ); array[ amount++ ] = x; } #include <iostream.h> /* main code */ int main() { simpleStack< int > aIntStack; int i = 100; while ( !aIntStack.full() ) aIntStack.push( i++ ); cout << "stack size: " << aIntStack.size() << endl; return 0; }
Related Topics: typename