Append to list

From: rhapsody (blurrynight_at_yahoo.com)
Date: 08/12/04 

Date: Wed, 11 Aug 2004 20:17:02 -0400

Can anybody give me clues of what is the correct way of appending node's
name to the output slist during the recursion of postOrder/2? I have
difficulties in getting the logic right. Below is the codes. Thanks!
Domains
btreeType = nil; btree(string, btreeType, btreeType)
slist = string*

Predicates
nondeterm postOrder(btreeType, slist)
buildtree(btreeType)

Clauses
postOrder(btree(Name,Tree1,Tree2), [H|T]) :-
postOrder(Tree1,T),
postOrder(Tree2,T),
write("Node : ", Name),
H = Name,
nl.

postOrder(btree(Name,nil,nil), [H|T]) :-
write("Node : ",Name),
H = Name,
nl.

buildtree(Atree):-
T1 = btree(a, nil, nil),
T2 = btree(c, nil, nil),
T3 = btree(e, nil, nil),
T4 = btree(b, T1, T2),
Atree = btree(d, T4, T3).

Goal
buildTree(Atree),postOrder(Atree,List),write("List : ", List).

Regards,
Stanly

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