RhodeCode

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

      template<typename _ReadMap>

      struct Constraints {

	void constraints() {

	  Value val = m[key];

	  val = m[key];

	  typename _ReadMap::Value own_val = m[own_key]; 

      /// Sets the value associated with a key.

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

      template<typename _ReferenceMap>

	void constraints() {

	  m[key] = val;

	  val  = m[key];

	  m[key] = ref;

	  ref = m[key];

	}

	typename _ReferenceMap::Key& own_key;

	typename _ReferenceMap::Value& own_val;

	Key& key;

	Value& val;

	_ReferenceMap& m;

      };

    };