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pl:prolog:pllib:rule_interpreter_4 [2019/06/27 15:50] (aktualna)
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 +====== Rule interpreter 4 ======
 +{{tag>​rules interpreter}}
 +===== Description =====
 +Specializing a rule interpreter
 +
 +**Source**: ​ The Art of Prolog
 +===== Download =====
 +Program source code: {{rule_interpreter_4.pl}}
 +===== Listing =====
 +<code prolog>
 +/*
 +        Rule interpreter for counting reductions
 +*/
 +
 +:- op(40,​xfy,&​).
 +:- op(30,​xf,​is_true).
 +
 +        solve(A,1) :-  fact(A).
 +        solve(A,N) :-  rule(A,​B,​Name),​ solve_body(B,​NB),​ N is NB+1.
 +
 +        solve_body(A&​B,​N) :-
 +           ​solve_body(A,​NA),​ solve_body(B,​NB),​ N is NA+NB.
 +        solve_body(A is_true,N) :-  solve(A,N).
 +
 +%        Sample rule base
 +
 +        rule(oven(Dish,​top),​pastry(Dish) is_true
 +           & size(Dish,​small) is_true,​place1).
 +        rule(oven(Dish,​middle),​pastry(Dish) is_true
 +           & size(Dish,​big) is_true,​place2).
 +        rule(oven(Dish,​middle),​main_meal(Dish) is_true,​place3).
 +        rule(oven(Dish,​bottom),​slow_cooker(Dish) is_true,​place4).
 +        rule(pastry(Dish),​type(Dish,​cake) is_true,​pastry1).
 +        rule(pastry(Dish),​type(Dish,​bread) is_true,​pastry2).
 +        rule(main_meal(Dish),​type(Dish,​meat) is_true,​main_meal).
 +        rule(slow_cooker(Dish),​type(Dish,​milk_pudding)
 +           ​is_true,​slow_cooker).
 +
 +        should_fold(solve(oven(D,​P),​N),​oven(D,​P,​N)).
 +        should_fold(solve(pastry(D),​N),​pastry(D,​N)).
 +        should_fold(solve(main_meal(D),​N),​main_meal(D,​N)).
 +        should_fold(solve(slow_cooker(D),​N),​slow_cooker(D,​N)).
 +        should_fold(solve(type(D,​P),​N),​type(D,​P,​N)).
 +        should_fold(solve(size(D,​P),​N),​size(D,​P,​N)).
 +
 +        should_unfold(solve_body(G,​N)).
 +        should_unfold(rule(A,​B,​Name)).
 +
 +        program(rule_interpreter,​[(solve(A1,​1) :-  fact(A1)),
 +           ​(solve(A2,​N) :-  rule(A2,​B,​Name),​ solve_body(B,​NB),​ N is NB+1)]).
 +
 +%        Program 18.5: Specializing a rule interpreter
 +</​code>​
 +===== Comments =====
  
pl/prolog/pllib/rule_interpreter_4.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)
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