1.3 Variant of the parser that builds trees

/* Variant of the depth-first, left-to-right parser
   that also builds trees in the form of lists of
   lists. It requires the grammar file to be loaded
   first.
   
   Here is how the parser is called:

| ?- parse(s, T, [the,dog,chased,the,cat], []).

T = [s,[np,[det,the],[n,dog]],[vp,[v,chased],[np,[det,the],[n,cat]]]] ? 

yes
*/


parse(Cat, [Cat,Firstword], [Firstword|Restwords], Restwords):-
    Cat ==> Firstword.

parse(Cat, [Cat|Tree], String, Rest ):-
   (Cat ==> Daughters),
   parserest(Daughters, Tree, String, Rest).

parserest((Cat, Cats),  [Tree, Resttree], String, Rest):-
   parse(Cat, Tree, String, Next),
   parserest(Cats, Resttree, Next, Rest).

parserest(Cat, Tree, String, Rest):-
   parse(Cat, Tree, String, Rest).