Re: Overloading Subscript operator

=?ISO-8859-1?Q?Erik_Wikstr=F6m?= <>
Mon, 02 Apr 2007 18:00:01 GMT
On 2007-04-02 19:40, raan wrote:

What I am trying to achieve here is depicted in the small program

// Wrapit.cpp : Defines the entry point for the console application.

#include "stdafx.h"
#include <map>
#include <list>

using namespace std;

class A

   string a;
   string b;
   string c;


class B

  string a;
  string b;
  string c;

    B(){cout << "B constructor is being called \n";}

class C
    map<string, A *> aobj;
    map<string, B *> bobj;

  C(){cout << "Constructor of C called \n";}

  template <class T>
  T& operator [] (string key)
     cout << "Operator [] called \n";
     return new A(); //if the key has a particular text in it return
new A
                     // otherwise return new B();


int _tmain(int argc, _TCHAR* argv[])
    C c;
    c["abcd"] = new A();
    c["efgh"] = new B();

    return 0;

Obviously the above program will give you compiler errors.

I am trying to put a wrapper around the maps. And the insertion to the
maps is done through an
(eg . c["abcd"] = new A()) overloaded [] operator. Further I want to
use just one [] version of the function, but inside I will determine
whether I should return a new A() or a new B(). The string I recieved
as argument will have enough information for me to decide which object
to be returned. How would i do it.

I'm 99.99% sure you can't. Not unless you make both A and B inherit from
a common base-class and return that. You must remember that templates
are compile-time constructs so they can't depend on anything that isn't
known at compiletime.

Erik Wikstr?m

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