Re: stl map key

andre <as@yahoo.com> wrote:


  I am aware that this doesn't exactly answer your question,
  but in case you find yourself doing this repeatedly and if
  you're sure that there's always a one-to-one relationship
  between keys and values, you might want to create a reversed
  map where keys and values are swapped.
  I have this in my toolbox:

    // Caution! I had to copy-paste this together from several
    // functions, so it might contain silly errors
    template< typename T1, typename T2 >
    inline void build_reverse_map(const std::map<T1,T2>& map, std::map<T2,T1>& reverse_map)
    {
      typedef std::map<T1,T2> map_type;
      typedef std::map<T2,T1> reverse_map_type;
      typedef typename reverse_map_type::value_type reverse_value_type;

      for( typename map_type::const_iterator it=map.begin(),
                                            end=map.end(); it!=end; ++it ) {
        assert( reverse_map.insert(reverse_value_type(it->second,it->first)).second );
      }
    }

  Use it like this:

    void f()
    {
      std::map<int,string> my_map;
      // fill 'my_map'
      std::map<string,int> my_reverse_map;
      build_reverse_map(my_map,my_reverse_map);
      // use reverse map
    }

  HTH,

  Schobi

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