definite_clause_grammar.hs

-- https://en.wikipedia.org/wiki/Definite_clause_grammar

-- http://cs.union.edu/~striegnk/learn-prolog-now/html/node59.html#subsec.l7.firstexample

-- This grammar allows sentences like "he likes her" and "he likes him", but not "her likes he" and "him likes him".

 sentence --> pronoun(subject), verb_phrase.
 verb_phrase --> verb, pronoun(object).
 pronoun(subject) --> [he].
 pronoun(subject) --> [she].
 pronoun(object) --> [him].
 pronoun(object) --> [her].
 verb --> [likes].

-- "the bat eats a cat"
​
 sentence(s(NP,VP)) --> noun_phrase(NP), verb_phrase(VP).
 noun_phrase(np(D,N)) --> det(D), noun(N).
 verb_phrase(vp(V,NP)) --> verb(V), noun_phrase(NP).
 det(d(the)) --> [the].
 det(d(a)) --> [a].
 noun(n(bat)) --> [bat].
 noun(n(cat)) --> [cat].
 verb(v(eats)) --> [eats]
 
 
 ----
 
s --> simple_s.
s --> simple_s conj s.
simple_s --> np,vp.
np --> det,n.
vp --> v,np.
vp --> v.
det --> [the].
det --> [a].
n --> [woman].
n --> [man].
v --> [shoots].
conj --> [and].
conj --> [or].
conj --> [but].