map const accessor

I wanted to access map in a const form. However the default [] accessor doesn't allow you to do that, because it will create a new entry in map if the thing you are looking for doesn't exist. This program describes the problem:

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

using namespace std;

class MyMapEncap {
  public:

  map<string,vector<int> > mymap;

  const vector<int> &getvec(string id) const {
    return mymap[id];
  }
};

int main() {
  MyMapEncap e;

  e.getvec("RAW");

}

The solution is to use the find method which returns an iterator to the thing your looking for in the above example like this:

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

using namespace std;

class MyMapEncap {
  public:

  map<string,vector<int> > mymap;

  const vector<int> &getvec(string id) const {
    return (*mymap.find(id)).second;
  }
};

int main() {
  MyMapEncap e;

  e.getvec("RAW");

}