% File: a.p
%       grammar for a shapes micro-world

:- ['process.p'].

sentence -->  cmmnd.
sentence -->  query.
sentence -->  [].

cmmnd -->  [place], indefArticle, color, [square], [at],
          number, number, [with], [side], number, ['.'].

cmmnd --> [place], indefArticle, color, [rectangle], [at], number, number,
          [of], [height], number, [and], [width], number, ['.'].

cmmnd --> [place], indefArticle, color, [circle], [at], number, number,
          [of], [radius], number, ['.'].

cmmnd -->  [stop], ['.'].

query --> [what], shapes, [are], [there], ['?'].

query --> [what], [color], shapes, [are], [present], ['?'].

query --> [are], [there], [any], color, shapes, [present], ['?'].

query --> [how], [big], [is], defArticle, shape, [at], number, number, ['?'].

defArticle --> [the].

indefArticle --> [a].
indefArticle --> [an].

color --> [red].
color --> [blue].
color --> [green].

number --> [N], { number(N) }.

shape --> [square].
shape --> [rectangle].
shape --> [circle].
shape --> [shape].

shapes --> [squares].
shapes --> [rectangles].
shapes --> [circles].
shapes --> [shapes].