Notes on computational linguistics.pdf - UCLA Department of ...

Stabler - Lx 185/209 2003
(19) The implementation of the LC recognizer:
/*
* file: lc.pl
*/
:- op(1200,xfx,: ˜ ). % this is our object language "if"
:- op(1100,xfx,? ˜ ). % metalanguage provability predicate
[] ? ˜ [].
(S0 ? ˜Goals0) :- infer(S0,Goals0,S,Goals), (S ? ˜Goals). infer(S,[-D,A|C],S,DC) :- (A : ˜ [D|Ds]), append(Ds,C,DC). % lc-complete
infer(S,[-D|C],S,DAC) :- (A : ˜ [D|Ds]), append(Ds,[-A|C],DAC). % lc
infer([W|S],[W|C],S,C). % shift-complete=scan
infer([W|S],C,S,[-W|C]). % shift
infer(S,[A|C],S,C) :- (A : ˜ []). % lc-e-complete
infer(S,C,S,[-A|C]) :- (A : ˜ []). % lc-e
append([],L,L).
append([E|L],M,[E|N]) :- append(L,M,N).
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