Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!psuvax1!psuvm!f0o
From: F0O@psuvm.psu.edu
Newsgroups: comp.lang.prolog
Subject: Deterministic predicate question
Message-ID: <90239.224751F0O@psuvm.psu.edu>
Date: 28 Aug 90 02:47:51 GMT
Organization: Penn State University
Lines: 32


    The build_board predicates will set up a beginning tic-tac-toe board.
The predicates work ok, but they are both non-deterministic.  However,
our old friend length is deterministic.
    I'm curious as to why length is deterministic where both of the
build_board predicates are not.  Also, is there a way to make one of the
build_board predicates deterministic, without using the cut?


    build_board1(10).
    build_board1(SquareNum) :-
         NextSquare = SquareNum + 1,
         build_board1(NextSquare),
         assert(board(SquareNum," ")).


    build_board2(10).
    build_board2(SquareNum) :-
         assert(board(SquareNum," ")),
         NextSquare = SquareNum + 1,
         build_board2(NextSquare).


    length([],0).
    length([_|T],Len) :-
         length(T,Tmp),
         Len = Tmp + 1.


                                       Thanks muchly,

                                                [Tim]