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Using Template Functions to Customize Library Behavior

March 2001/Using Template Functions to Customize Library Behavior/Listing 1

Listing 1: Providing a user-definable policy via a macro

//---- begin file library.h ----

#  define CLASS_POLICY "default policy"

//---- begin file container.h ----

#include "library.h"
#include <string>
#include <iostream>

template <class ElementType>
class MyContainer {
   MyContainer(const std::string iName) : instanceName(iName) 
   // class implementation
   // ...
   // performs the policy
   void doPolicy();
   // a service that uses the policy
   void performService() { doPolicy(); }
   const std::string instanceName;

// elements for example's sake
template<class T>
struct Element1 {
// ...

template<class T>
struct Element2 {
// ...

template <class ElementType>
void MyContainer<ElementType>::doPolicy() 
    std::cout << "Policy is: " << CLASS_POLICY << std::endl;

//---- begin file user.cpp ----

#include "container.h"

int main() {
   MyContainer<Element1<int> > c("object1");

   return 0;
— End of Listing —

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