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esad/test.pl

Created June 18, 2019 11:53
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Reversible dcg rules
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test.pl
:- op(1200, xfx, <-->).
:- use_module(library(dcg/basics), [digit//1]).
conj_rev(Term, Term) :- \+ Term = (_, _).
conj_rev((Term1,Term2), (Term2, T)) :- conj_rev(Term1, T).
term_expansion(<-->(X, Y), T) :- conj_rev(Y, YRev), dcg_translate_rule(X --> YRev, T).
term_expansion(<-->(X, Y), T) :- dcg_translate_rule(X --> Y, T).
year(Y) <--> digit(D0), digit(D1), digit(D2), digit(D3), { number_codes(Y, [D0,D1,D2,D3]) }.
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