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Logtalk - Object oriented extension to Prolog
Release 2.15.3
Copyright (c) 1998-2003 Paulo Moura. All Rights Reserved.
| ?- square::nsides(N).
! error(
existence_error(predicate_declaration, nsides(_)),
square::nsides(N),
user)
| ?- q1::(color(Color), side(Side), position(X, Y)).
Color = red
Side = 1
X = 0
Y = 0
yes
| ?- q2::(side(Side), area(Area), perimeter(Perimeter)).
Side = 3
Area = 9
Perimeter = 12
