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pl:prolog:pllib:grammar2clauses [2019/06/27 15:50] (aktualna) |
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| + | ====== Grammar2clauses ====== | ||
| + | {{tag>rules DCG}} | ||
| + | ===== Description ===== | ||
| + | Translating grammar rules to Prolog clauses | ||
| + | |||
| + | **Source**: The Art of Prolog | ||
| + | ===== Download ===== | ||
| + | Program source code: {{grammar2clauses.pl}} | ||
| + | ===== Listing ===== | ||
| + | <code prolog> | ||
| + | /* | ||
| + | translate(Grammar,Program) :- | ||
| + | Program is the Prolog equivalent of the context-free | ||
| + | grammar Grammar. | ||
| + | */ | ||
| + | |||
| + | :- op(40,xfx,\). | ||
| + | |||
| + | translate([Rule|Rules],[Clause|Clauses]) :- | ||
| + | translate_rule(Rule,Clause), | ||
| + | translate(Rules,Clauses). | ||
| + | translate([ ],[ ]). | ||
| + | |||
| + | /* | ||
| + | translate_rule(GrammarRule,PrologClause) :- | ||
| + | PrologClause is the Prolog equivalent of the grammar | ||
| + | rule GrammarRule. | ||
| + | */ | ||
| + | translate_rule((Lhs --> Rhs),(Head :- Body)) :- | ||
| + | translate_head(Lhs,Head,Xs\Ys), | ||
| + | translate_body(Rhs,Body,Xs\Ys),!. | ||
| + | |||
| + | translate_head(A,A1,Xs) :- | ||
| + | translate_goal(A,A1,Xs). | ||
| + | |||
| + | translate_body((A,B),(A1,B1),Xs\Ys) :- | ||
| + | !, translate_body(A,A1,Xs\Xs1), translate_body(B,B1,Xs1\Ys). | ||
| + | translate_body(A,A1,Xs) :- | ||
| + | translate_goal(A,A1,Xs). | ||
| + | |||
| + | translate_goal(A,A1,DList) :- | ||
| + | nonterminal(A), functor(A1,A,1), arg(1,A1,DList). | ||
| + | translate_goal(Terms,connect(Terms,S),S) :- | ||
| + | terminals(Terms). | ||
| + | |||
| + | non_terminal(A) :- atom(A). | ||
| + | |||
| + | terminals(Xs) :- list(Xs). | ||
| + | |||
| + | list([]). | ||
| + | list([X|Xs]) :- list(Xs). | ||
| + | |||
| + | % Program 18.9: Translating grammar rules to Prolog clauses | ||
| + | </code> | ||
| + | ===== Comments ===== | ||
