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Logtalk - Object oriented extension to Prolog
Release 2.23.0

Copyright (c) 1998-2005 Paulo Moura.  All Rights Reserved.
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% start by loading the "assignvars" category:

| ?- logtalk_load(library(assignvars)).
...


% now you are ready for loading the example:

| ?- logtalk_load(assignvars(loader)).
...


% rectangle example:

?- rectangle(2, 3, _)::(init, position(X0, Y0), move(3, 7), position(X1, Y1), move(2, 5), position(X2, Y2)).

X0 = 0
Y0 = 0
X1 = 3
Y1 = 7
X2 = 2
Y2 = 5 

Yes


% finite state machine example:

| ?- fsm(T, I, F), fsm(T, I, F)::recognise([0,1,1,2,1,2,0]).

red-0-red
red-1-green
green-1-yellow
yellow-2-red
red-1-green
green-2-red
red-0-red

T = [red-0-red, red-1-green, red-2-red, yellow-0-red, yellow-1-green, yellow-2-red, green-0-yellow, ... -... -yellow, ... -...]
I = red
F = [red] 

Yes


% finite state machine example:

| ?- fsm(T, I, F), !, fsm(T, I, F)::recognise([0,1,1,2,1,2,1,0]).

red-0-red
red-1-green
green-1-yellow
yellow-2-red
red-1-green
green-2-red
red-1-green
green-0-yellow
backtracking...
backtracking...
backtracking...
backtracking...
backtracking...
backtracking...
backtracking...
backtracking...

No