C++ map::find for pair as key

Question

I have a map of pair as key and bool as value. When i try to find a certain pair that is already included using map::find method, it's not finding any item. What do i do wrong?

I tried to implement a comparator class and set it as key_comp in map, but I'm not sure i did it right. Is this the solve?

I am working in VS12, I attached a photo with the debugging, you shall understand much more from that:

Answer 1

You are calling find with pair<char *, char*>(0x00ffc468, 0x00ffbdb0) . There is no such pair in the set, so find returns end .

Your code compares char * 's, which checks if they point to the same place in memory, not whether they point to identical content. You should probably use std::string instead of char * rather than reinventing wheels.

Here's an example of a possible comparison function you could use if you insist on doing so:

bool less(
    std::pair<char *, char *> const& p1,
    std::pair<char *, char *> const& p2)
{
    int i = strcmp (p1.first, p2.first);
    if (i < 0)
        return true;
    if (i > 0)
        return false;
    return strcmp (p1.second, p2.second) < 0;
}

Answer 2

If you must use std:pair<char*, char*> as key in your map, you can use the following functor while creating the map.

struct MyCompare
{
   bool operator()(std::pair<char const*, char const*> const& lhs,
                   std::pair<char const*, char const*> const& rhs)
   {
      int n1 = strcmp(lhs.first, rhs.first);
      if ( n1 != 0 )
      {
         return n1 < 0;
      }
      return (strcmp(lhs.second, rhs.second) < 0);
   }
};


typedef std::map<std::pair<char*,char*>, int, MyCompare> MyMap;
MyMap myMap;