% Top-Down-Chart-Parser mit Vollstaendigkeitsvermerk
% Simon Clematide "Programmiertechniken in der Computerlinguistik II" Sommer 2005
% Unterlagen dazu im Skript

/* Anfragebeispiele
?- clear_chart, parse(vp, [chased,a,dog,with,a,bone]-[]).

Geschwaetziger Parser

?- clear_chart, C=vp,verbose_parse(C, [chased,a,dog,with,a,bone]-[]).
*/

% Grammatik und Lexikon

rule(s, [np,vp]).
rule(np, [det,n]).
rule(np, [det,n,pp]).
rule(vp, [v,np]).
rule(vp, [v,np,pp]).
rule(pp, [p,np]).

word(det, a).
word(p, with).
word(n, dog). 
word(n, bone). 
word(v, chased). 





% parse/2: Parsen einer Kategorie C

parse(C, [Word|S]-S) :-
   word(C, Word).

parse(C, S-Rest) :-
   complete(C, S),
   !,
   edge(C, S, Rest).

parse(C, S-Rest) :-
   rule(C, RHS),
   parse_daughters(RHS, S-S1),
   asserta(edge(C, S, S1)),
   S1 = Rest.

parse(C,S-_) :-
   asserta(complete(C,S)),
   fail.


% parse_daughters/2: Parsen einer 
% Liste von Kategorien

parse_daughters([C|Cs], S-Rest) :-
   parse(C, S-S1),
   parse_daughters(Cs, S1-Rest).

parse_daughters([], S-S).


% Vollstaendigkeitsvermerk

:- dynamic complete/2.

% Kanten
:- dynamic edge/3.

% Chart saeubern
clear_chart :-
	retract(edge(_,_,_)),
	fail.
clear_chart :-
	retract(complete(_,_)),
	fail.
clear_chart.








verbose_parse(C, [Word|S]-S) :-
   word(C, Word).

verbose_parse(C, S-Rest) :-
   complete(C, S),
   !,
   edge(C, S, Rest),
   format("FOUND IN CHART: ~p~N",[edge(C,S,Rest)]).

verbose_parse(C, S-Rest) :-
   rule(C, RHS),
   verbose_parse_daughters(RHS, S-S1),
   asserta(edge(C, S, S1)),
   format("ADDED IN CHART: ~p~N",[edge(C, S, S1)]),
   S1 = Rest.

verbose_parse(C,S-_) :-
   asserta(complete(C,S)),
   format("COMPLETED CATEGORY '~p' STARTING ON ~p~N",[C,S]),
   fail.


% verbose_parse_daughters/2: Parsen einer 
% Liste von Kategorien

verbose_parse_daughters([C|Cs], S-Rest) :-
   verbose_parse(C, S-S1),
   verbose_parse_daughters(Cs, S1-Rest).

verbose_parse_daughters([], S-S).