%%%%%%%%%%%%%%%%%%%%%%%%% Header
:- op(800, fx, (def_object)).
:- op(800, fx, (end_def)).
:- op(401, xfx, (::)).
:- op(600, xfx, (isa)).
%%%%%%%%%%%%%%%%%%%%%%%%% OBJECT.op
'OBJECT'(defines_property(A), B) :-
	defines_prop(B, A).
'OBJECT'(parent(A), B) :-
	B isa A.
%%%%%%%%%%%%%%%%%%%%%%%%% sample.op
:- op(300, fx, dummyop).
dummyop 2.

% desk isa OBJECT
desk(d_len(70), A).
desk(d_num(3), A).
desk(d_width(30), A).
desk(d_tot_area(A), B) :-
	B :: d_num(C),
	B :: d_len(D),
	B :: d_width(E),
	A is C * D * E.

% my_desk isa desk
my_desk(d_num(4), A).

% his_desk isa desk
his_desk(d_len(50), A).

% room isa OBJECT
room(d_area(A), B) :-
	my_desk :: d_tot_area(C),
	his_desk :: d_tot_area(D),
	A is C + D.


desk isa 'OBJECT'.
my_desk isa desk.
his_desk isa desk.
room isa 'OBJECT'.

object('OBJECT').
object(desk).
object(my_desk).
object(his_desk).
object(room).

defines_prop('OBJECT', defines_property(A)).
defines_prop('OBJECT', parent(A)).
defines_prop(desk, d_len(A)).
defines_prop(desk, d_num(A)).
defines_prop(desk, d_width(A)).
defines_prop(desk, d_tot_area(A)).
defines_prop(my_desk, d_num(A)).
defines_prop(his_desk, d_len(A)).
defines_prop(room, d_area(A)).

call_object('OBJECT', defines_property(A), B) :-
	'OBJECT'(defines_property(A), B).
call_object('OBJECT', parent(A), B) :-
	'OBJECT'(parent(A), B).
call_object(desk, d_len(A), B) :-
	desk(d_len(A), B).
call_object(desk, d_num(A), B) :-
	desk(d_num(A), B).
call_object(desk, d_width(A), B) :-
	desk(d_width(A), B).
call_object(desk, d_tot_area(A), B) :-
	desk(d_tot_area(A), B).
call_object(my_desk, d_num(A), B) :-
	my_desk(d_num(A), B).
call_object(his_desk, d_len(A), B) :-
	his_desk(d_len(A), B).
call_object(room, d_area(A), B) :-
	room(d_area(A), B).