Created
November 15, 2010 18:18
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AI::Prologのバックトラックを、そのままイテレータとして使用して、「4桁の数字に3回四則演算を行う RPN」を自動生成してみた例。遅い! あと、Prolog部の「formula/1」の定義のカット(!)を取ると帰ってこなくなる。ところが、SWI-Prolog等では帰ってくる。再帰最適化の違いのせい??
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#!/usr/bin/perl | |
use strict; | |
use warnings; | |
use AI::Prolog; | |
use 5.010; | |
my $database =<< 'END_PROLOG'; | |
append([], Z, Z). | |
append([W|X1], Y, [W|Z1]) :- append(X1, Y, Z1). | |
length([], 0). | |
length([X|Xs], N) :- length(Xs, N1), N is N1 + 1. | |
formula([D]) :- digit(D). | |
formula(X) :- append(F1, FandO, X), | |
append(F2, [O], FandO), | |
operator(O), | |
formula(F1), | |
formula(F2). | |
formula7(X) :- length(X, 7), !, formula(X). | |
digit(0). | |
digit(1). | |
digit(2). | |
digit(3). | |
digit(4). | |
digit(5). | |
digit(6). | |
digit(7). | |
digit(8). | |
digit(9). | |
operator("+"). | |
operator("-"). | |
operator("*"). | |
operator("/"). | |
END_PROLOG | |
my $prolog = AI::Prolog->new($database); | |
$prolog->query("formula7(X)."); | |
while (my $result = $prolog->results) { | |
say join " ", @{$result->[1]}; | |
} |
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