Finding Words

% find_word(+Word,+Tree,-LexEntry)
%  Finds Word in Tree retrieving LexEntry.
find_word([H|T],Tree,LexEntry) :-
   member([H|Branches],Tree),
   find_word(T,Branches,LexEntry).

find_word([],Tree,LexEntry) :-
   member(LexEntry,Tree),
   \+ (LexEntry = [_|_]).

• If the first clause: if the first letter of the word is the same as the first element of a branch, then recurse into the branch with the remainder of the word,
• When there are no more letters, Tree is the tail of a branch, consisting of (we hope) the lexical entry and possibly other branches.