c++ unordered_map compiling issue with g++

Question

I am using g++ in Ubuntu

g++ (Ubuntu 4.4.3-4ubuntu5) 4.4.3

I have this code

#include<unordered_map>
using namespace std;

bool ifunique(char *s){
  unordered_map<char,bool> h;
  if(s== NULL){
    return true;
  }
  while(*s){
    if(h.find(*s) != h.end()){
      return false;
    }
    h.insert(*s,true);
    s++;
  }
  return false;
}

when I compile using

g++ mycode.cc

I got error

 error: 'unordered_map' was not declared in this scope

Am I missing something?

Answer 1

If you don't want to to compile in C++0x mode, changing the include and using directive to

#include <tr1/unordered_map>
using namespace std::tr1;

should work

Answer 2

In GCC 4.4.x, you should only have to #include <unordered_map>, and compile with this line:

g++ -std=c++0x source.cxx

More information about C++0x support in GCC.

edit regarding your problem

You have to do std::make_pair<char, bool>(*s, true) when inserting.

Also, your code would only insert a single character (the dereferencing via *s). Do you intend to use a single char for a key, or did you mean to store strings?