/*	
    lookup(Key,Dictionary,Value) :-
	Dictionary contains the value indexed under Key.
	Dictionary is represented as an ordered binary tree.

*/

	lookup(Key,dict(Key,X,Left,Right),Value) :-
		!, X = Value.
	lookup(Key,dict(Key1,X,Left,Right),Value) :-
		Key < Key1 , lookup(Key,Left,Value).
	lookup(Key,dict(Key1,X,Left,Right),Value) :-
		Key > Key1, lookup(Key,Right,Value).

%	Program 15.9: Dictionary lookup in a binary tree