% File: b.p
%       grammar for a shapes micro-world
%       pseudo-code for semantic action added

:- ['process.p'].

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

cmmnd -->  [place], indefArticle, color, [square], [at],
          number, number, [with], [side], number, ['.'].
/*
          {
          Add a square to the knowledge base at give (x,y) coordinates.
          Article may be either 'a' or 'an'; color red, blue, or green.
          }
*/

cmmnd --> [place], indefArticle, color, [rectangle], [at], number, number,
          [of], [height], number, [and], [width], number, ['.'].
/*
          {
          Add a rectangle ...
          }
*/

cmmnd --> [place], indefArticle, color, [circle], [at], number, number,
          [of], [radius], number, ['.'].
/*
          {
          Add a circle ...
          }
*/

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

query --> [what], shapes, [are], [there], ['?'].
/*
          {
          enumerate the specified objects.
          }
*/
query --> [what], [color], shapes, [are], [present], ['?'].
/*
          {
          respond with the colors of the specified shape.
          }
*/

query --> [are], [there], [any], color, shapes, [present], ['?'].
/*
          {
          respond with yes/no
          }
*/

query --> [how], [big], [is], defArticle, shape, [at], number, number, ['?'].
/*
          {
          respond with length for squares, height and width for
          rectangles, radius for circles
          }
*/

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].