Question

I am writing a code which uses templates to support int datatype and char* datatype. lets say

struct node {
    KeyType key;
    struct node *next;
};

And this is sorted linked list node, so whenever I insert node, I have to compare. For this I created one header file comparison.h, in which I have defined comparison operation like

LT(a,b)..
GT(a,b)..

And when I use node<int> I define LT(a, b) as a<b and in case of node<char*> strncmp(a, b, SIZE) ( Using macro I switch the definition )
So Is there any way by which I minimally interfere this comparison.h. What should be the better ways of using comparison or specific operations specific to datatypes when using templates ?

Answer 1

Use template specialization. For example:

#include <iostream>
#include <string>
using namespace std;

template <class T>
class node {
    T data;
  public:
    node(){}
    static bool GT (const T& first, const T& second);
};

template <class T>
bool node<T>::GT(const T &first, const T &second)
{
    std::cout << "general use" << std::endl;
    return first > second;
}

template <>
bool node<string>::GT(const string &first, const string &second)
{
    std::cout << "called from a string" << std::endl;
    return first.compare(second)>0;
}

int main () {
  std::cout << node<int>::GT(10,20) << std::endl;
  std::cout << node<string>::GT("Hello","World") << std::endl;
  return 0;
}

The output will be:

general use
0
called from a string
0