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pl:prolog:pllib:partial_reduction [2019/06/27 15:50] |
pl:prolog:pllib:partial_reduction [2019/06/27 15:50] (aktualna) |
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| + | ====== Partial reduction ====== | ||
| + | {{tag>metainterpreter}} | ||
| + | ===== Description ===== | ||
| + | A simple partial reduction system | ||
| + | |||
| + | **Source**: The Art of Prolog | ||
| + | ===== Download ===== | ||
| + | Program source code: {{partial_reduction.pl}} | ||
| + | ===== Listing ===== | ||
| + | <code prolog> | ||
| + | /* | ||
| + | process(Program, RedProgram) :- | ||
| + | Partially reduce each of the clauses in Program to produce | ||
| + | RedProgram. | ||
| + | */ | ||
| + | process(Prog,NewProg) :- | ||
| + | findall(PCl,(member(Cl,Prog),preduce(Cl,PCl)),NewProg). | ||
| + | |||
| + | test(Name,Program) :- | ||
| + | program(Name,Clauses), process(Clauses,Program). | ||
| + | |||
| + | /* | ||
| + | preduce(Goal,Residue) :- | ||
| + | Partially reduce Goal to leave the residue Residue. | ||
| + | */ | ||
| + | preduce((A :- B),(PA :- PB)) :- | ||
| + | !, preduce(B,PB), preduce(A,PA). | ||
| + | preduce(true,true) :- !. | ||
| + | preduce((A,B),Res) :- | ||
| + | !, preduce(A,PA), preduce(B,PB), combine(PA,PB,Res). | ||
| + | preduce(A,B) :- should_fold(A,B), !. | ||
| + | preduce(A,Residue) :- | ||
| + | should_unfold(A), !, clause(A,B), preduce(B,Residue). | ||
| + | preduce(A,A). | ||
| + | |||
| + | combine(true,B,B) :- !. | ||
| + | combine(A,true,A) :- !. | ||
| + | combine(A,B,(A,B)). | ||
| + | |||
| + | % Program 18.3: A simple partial reduction system | ||
| + | </code> | ||
| + | ===== Comments ===== | ||
