Re: map problem

From:
csaba.trucza@gmail.com
Newsgroups:
comp.lang.c++.moderated
Date:
Thu, 26 Mar 2009 13:36:29 CST
Message-ID:
<f0b7dd96-fc7d-4976-8556-bc269d6ec09a@p11g2000yqe.googlegroups.com>

    map<char*, vector<char*> >::iterator it2 = data_container.find( "dynamic_selection" );
    if( it2==data_container.end() )
    {
        printf("NOT FOUND!\n");
    }
    else
   { printf("FOUND\n");
   printf("Size:%d\n", (*it2).second.size() );
   }

This always prints "NOT FOUND".

I can't see what's wrong!


At a guess it is because you are storing pointers. Two identical strings
will have different addresses unless they are the same string.


My first response was the same: char*'s will be compared as pointers.

Using Visual Studio 2008 I ran the following code, which as far as I
see reconstructs the OP's problem.

#include <map>
#include <vector>
#include <iostream>

using namespace std;

int main()
{
    map<char*, vector<char*> > data;

    data["foo"] = vector<char*>();
    data["foo"].push_back("foo.bar");
    data["foo"].push_back("foo.baz");

    data["bar"] = vector<char*>();
    data["bar"].push_back("bar.bar");
    data["bar"].push_back("bar.baz");

    if (data.find("foo") == data.end())
        cout << "not found" << endl;
    else
        cout << "found" << endl;

}

Strangely enough the output is "found". Anyone has an explanation?

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