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+====== Rule interpreter 3 ======
+{{tag>rule interpreter framework}}
+===== Description =====
+A skeleton two-level rule interpreter
+**Source**:  The Art of Prolog
+===== Download =====
+Program source code: {{rule_interpreter_3.pl}}
+===== Listing =====
+<code prolog>
+/*
+       monitor(Goal) :-
+           Succeeds if a result of yes is returned from solving Goal
+          at the solve level, or when the end of the computation is reached.
+*/
+:- op(40,xfy,&).
+:- op(30,xf,is_true).
+       monitor(Goal) :-  solve(Goal,Result), filter(Result).
+       monitor(Goal).
+       filter(yes).
+       % filter(no)   fail.
+/*
+       solve(Goal,Result) :-
+           Given a set of rules of the form rule(A,B,Name), Goal has
+           Result yes if it follows from the rules and no if it does not.
+*/
+       solve(A,yes) :-  fact(A).
+       solve(A,Result) :-  rule(A,B,Name), solve_body(B,Result).
+       solve(A,no).
+       solve_body(A&B,Result) :-
+           solve(A,ResultA), solve_and(ResultA,B,Result).
+       solve_body(A is_true,Result) :-   solve(A,Result).
+       solve_and(no,A,no).
+       solve_and(yes,B,Result) :- solve(B,Result).
+%   Program 17.18: A skeleton two-level rule interpreter
+</code>
+===== Comments =====

pl/prolog/pllib/rule_interpreter_3.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)

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