/* lookup(X, Y, Z) is true if the entry X in the sorted tree Y has */
/* data Z. Entries can be added, queried or verified. */
lookup(Key, dict(Key, Value, _, _), Value):-!.
lookup(Key, dict(Key1, _, Left, _), Value):-
Key < Key1, !, lookup(Key, Left, Value).
lookup(Key, dict(Key1, _, _, Right), Value):-
Key > Key1, lookup(Key, Right, Value).
test(X):-
lookup("a", Dictionary, 1), /* Add a = 1 */
lookup("b", Dictionary, 2), /* Add b = 2 */
lookup("a", Dictionary, X), /* Query a */
\+ lookup("a", Dictionary, 2), /* Verify a != 2 */
lookup("a", Dictionary, 1). /* Verify a = 1 */