1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
;;;======================================================
;;; Cannibals and Missionaries Problem
;;;
;;; Another classic AI problem. The point is
;;; to get three cannibals and three missionaries
;;; across a stream with a boat that can only
;;; hold two people. If the cannibals outnumber
;;; the missionaries on either side of the stream,
;; then the cannibals will eat the missionaries.
;;;
;;; CLIPS Version 6.01 Example
;;;
;;; To execute, merely load, reset and run.
;;;======================================================
(defmodule MAIN
(export deftemplate status)
(export defglobal initial-missionaries initial-cannibals))
;;;*************
;;;* TEMPLATES *
;;;*************
;;; The status facts hold the state
;;; information of the search tree.
(deftemplate MAIN::status
(slot search-depth (type INTEGER) (range 1 ?VARIABLE))
(slot parent (type FACT-ADDRESS SYMBOL) (allowed-symbols no-parent))
(slot shore-1-missionaries (type INTEGER) (range 0 ?VARIABLE))
(slot shore-1-cannibals (type INTEGER) (range 0 ?VARIABLE))
(slot shore-2-missionaries (type INTEGER) (range 0 ?VARIABLE))
(slot shore-2-cannibals (type INTEGER) (range 0 ?VARIABLE))
(slot boat-location (type SYMBOL) (allowed-values shore-1 shore-2))
(slot last-move (type STRING)))
;;;*****************
;;;* INITIAL STATE *
;;;*****************
(defglobal MAIN ?*initial-missionaries* = 3
?*initial-cannibals* = 3)
(deffacts MAIN::initial-positions
(status (search-depth 1)
(parent no-parent)
(shore-1-missionaries ?*initial-missionaries*)
(shore-2-missionaries 0)
(shore-1-cannibals ?*initial-cannibals*)
(shore-2-cannibals 0)
(boat-location shore-1)
(last-move "No move.")))
(deffacts MAIN::boat-information
(boat-can-hold 2))
;;;****************************************
;;;* FUNCTION FOR MOVE DESCRIPTION STRING *
;;;****************************************
(deffunction MAIN::move-string (?missionaries ?cannibals ?shore)
(switch ?missionaries
(case 0 then
(if (eq ?cannibals 1)
then (format nil "Move 1 cannibal to %s.%n" ?shore)
else (format nil "Move %d cannibals to %s.%n" ?cannibals ?shore)))
(case 1 then
(switch ?cannibals
(case 0 then
(format nil "Move 1 missionary to %s.%n" ?shore))
(case 1 then
(format nil "Move 1 missionary and 1 cannibal to %s.%n" ?shore))
(default then
(format nil "Move 1 missionary and %d cannibals to %s.%n"
?cannibals ?shore))))
(default
(switch ?cannibals
(case 0 then
(format nil "Move %d missionaries to %s.%n" ?missionaries ?shore))
(case 1 then
(format nil "Move %d missionaries and 1 cannibal to %s.%n"
?missionaries ?shore))
(default then
(format nil "Move %d missionary and %d cannibals to %s.%n"
?missionaries ?cannibals ?shore))))))
;;;***********************
;;;* GENERATE PATH RULES *
;;;***********************
(defrule MAIN::shore-1-move
?node <- (status (search-depth ?num)
(boat-location shore-1)
(shore-1-missionaries ?s1m)
(shore-1-cannibals ?s1c)
(shore-2-missionaries ?s2m)
(shore-2-cannibals ?s2c))
(boat-can-hold ?limit)
=>
(bind ?max-missionaries (min ?s1m ?limit))
(loop-for-count (?missionaries 0 ?max-missionaries)
(bind ?min-cannibals (max 0 (- 1 ?missionaries)))
(bind ?max-cannibals (min ?s1c (- ?limit ?missionaries)))
(loop-for-count (?cannibals ?min-cannibals ?max-cannibals)
(duplicate ?node (search-depth =(+ 1 ?num))
(parent ?node)
(shore-1-missionaries (- ?s1m ?missionaries))
(shore-1-cannibals (- ?s1c ?cannibals))
(shore-2-missionaries (+ ?s2m ?missionaries))
(shore-2-cannibals (+ ?s2c ?cannibals))
(boat-location shore-2)
(last-move (move-string ?missionaries ?cannibals shore-2))))))
(defrule MAIN::shore-2-move
?node <- (status (search-depth ?num)
(boat-location shore-2)
(shore-1-missionaries ?s1m)
(shore-1-cannibals ?s1c)
(shore-2-missionaries ?s2m)
(shore-2-cannibals ?s2c))
(boat-can-hold ?limit)
=>
(bind ?max-missionaries (min ?s2m ?limit))
(loop-for-count (?missionaries 0 ?max-missionaries)
(bind ?min-cannibals (max 0 (- 1 ?missionaries)))
(bind ?max-cannibals (min ?s2c (- ?limit ?missionaries)))
(loop-for-count (?cannibals ?min-cannibals ?max-cannibals)
(duplicate ?node (search-depth =(+ 1 ?num))
(parent ?node)
(shore-1-missionaries (+ ?s1m ?missionaries))
(shore-1-cannibals (+ ?s1c ?cannibals))
(shore-2-missionaries (- ?s2m ?missionaries))
(shore-2-cannibals (- ?s2c ?cannibals))
(boat-location shore-1)
(last-move (move-string ?missionaries ?cannibals shore-1))))))
;;;******************************
;;;* CONSTRAINT VIOLATION RULES *
;;;******************************
(defmodule CONSTRAINTS
(import MAIN deftemplate status))
(defrule CONSTRAINTS::cannibals-eat-missionaries
(declare (auto-focus TRUE))
?node <- (status (shore-1-missionaries ?s1m)
(shore-1-cannibals ?s1c)
(shore-2-missionaries ?s2m)
(shore-2-cannibals ?s2c))
(test (or (and (> ?s2c ?s2m) (<> ?s2m 0))
(and (> ?s1c ?s1m) (<> ?s1m 0))))
=>
(retract ?node))
(defrule CONSTRAINTS::circular-path
(declare (auto-focus TRUE))
(status (search-depth ?sd1)
(boat-location ?bl)
(shore-1-missionaries ?s1m)
(shore-1-cannibals ?s1c)
(shore-2-missionaries ?s2m)
(shore-2-cannibals ?s2c))
?node <- (status (search-depth ?sd2&:(< ?sd1 ?sd2))
(boat-location ?bl)
(shore-1-missionaries ?s1m)
(shore-1-cannibals ?s1c)
(shore-2-missionaries ?s2m)
(shore-2-cannibals ?s2c))
=>
(retract ?node))
;;;*********************************
;;;* FIND AND PRINT SOLUTION RULES *
;;;*********************************
(defmodule SOLUTION
(import MAIN deftemplate status)
(import MAIN defglobal initial-missionaries initial-cannibals))
(deftemplate SOLUTION::moves
(slot id (type FACT-ADDRESS SYMBOL) (allowed-symbols no-parent))
(multislot moves-list
(type STRING)))
(defrule SOLUTION::recognize-solution
(declare (auto-focus TRUE))
?node <- (status (parent ?parent)
(shore-2-missionaries ?m&:(= ?m ?*initial-missionaries*))
(shore-2-cannibals ?c&:(= ?c ?*initial-cannibals*))
(last-move ?move))
=>
(retract ?node)
(assert (moves (id ?parent) (moves-list ?move))))
(defrule SOLUTION::further-solution
?node <- (status (parent ?parent)
(last-move ?move))
?mv <- (moves (id ?node) (moves-list $?rest))
=>
(modify ?mv (id ?parent) (moves-list ?move ?rest)))
(defrule SOLUTION::print-solution
?mv <- (moves (id no-parent) (moves-list "No move." $?m))
=>
(retract ?mv)
(printout t t "Solution found: " t t)
(progn$ (?move ?m) (printout t ?move)))
|
