RhodeCode

      typedef T Value;

      /// Returns the value associated with a key.

      /// \bug Value shouldn't need to be default constructible.

      ///

      Value operator[](const Key &) const {return Value();}

      };

    };

    /// Read/writable map concept.

    ///

    template<typename K, typename T>

    /// Dereferable map concept

    /// Dereferable map concept.

    ///

    template<typename K, typename T, typename R, typename CR>

    class ReferenceMap : public ReadWriteMap<K,T>

    {

    public:

    protected:

      Value tmp;

    public:

      Reference operator[](const Key &) { return tmp; }

      ConstReference operator[](const Key &) const { return tmp; }

      /// Sets the value associated with a key.

      void set(const Key &k,const Value &t) { operator[](k)=t; }

      template<typename _ReferenceMap>

      struct ReferenceMapConcept {

	void constraints() {