/* 8_puzzle.pl */
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%% A* Algorithm
%%%
%%%
%%% Nodes have form S#D#F#A
%%% where S describes the state or configuration
%%% D is the depth of the node
%%% F is the evaluation function value
%%% A is the ancestor list for the node
:- op(400,yfx,'#'). /* Node builder notation */
solve(State,Soln) :- f_function(State,0,F),
search([State#0#F#[]],S), reverse(S,Soln).
f_function(State,D,F) :- h_function(State,H),
F is D + H.
search([State#_#_#Soln|_], Soln) :- goal(State).
search([B|R],S) :- expand(B,Children),
insert_all(Children,R,Open),
search(Open,S).
insert_all([F|R],Open1,Open3) :- insert(F,Open1,Open2),
insert_all(R,Open2,Open3).
insert_all([],Open,Open).
insert(B,Open,Open) :- repeat_node(B,Open), ! .
insert(B,[C|R],[B,C|R]) :- cheaper(B,C), ! .
insert(B,[B1|R],[B1|S]) :- insert(B,R,S), !.
insert(B,[],[B]).
repeat_node(P#_#_#_, [P#_#_#_|_]).
cheaper( _#_#F1#_ , _#_#F2#_ ) :- F1 < F2.
expand(State#D#_#S,All_My_Children) :-
bagof(Child#D1#F#[Move|S],
(D1 is D+1,
move(State,Child,Move),
f_function(Child,D1,F)),
All_My_Children).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%% 8-puzzle solver
%%%
%%%
%%% State have form A/B/C/D/E/F/G/H/I
%%% where {A,...,I} = {0,...,8}
%%% 0 represents the empty tile
%%%
goal(1/2/3/8/0/4/7/6/5).
%%% The puzzle moves
left( A/0/C/D/E/F/H/I/J , 0/A/C/D/E/F/H/I/J ).
left( A/B/C/D/0/F/H/I/J , A/B/C/0/D/F/H/I/J ).
left( A/B/C/D/E/F/H/0/J , A/B/C/D/E/F/0/H/J ).
left( A/B/0/D/E/F/H/I/J , A/0/B/D/E/F/H/I/J ).
left( A/B/C/D/E/0/H/I/J , A/B/C/D/0/E/H/I/J ).
left( A/B/C/D/E/F/H/I/0 , A/B/C/D/E/F/H/0/I ).
up( A/B/C/0/E/F/H/I/J , 0/B/C/A/E/F/H/I/J ).
up( A/B/C/D/0/F/H/I/J , A/0/C/D/B/F/H/I/J ).
up( A/B/C/D/E/0/H/I/J , A/B/0/D/E/C/H/I/J ).
up( A/B/C/D/E/F/0/I/J , A/B/C/0/E/F/D/I/J ).
up( A/B/C/D/E/F/H/0/J , A/B/C/D/0/F/H/E/J ).
up( A/B/C/D/E/F/H/I/0 , A/B/C/D/E/0/H/I/F ).
right( A/0/C/D/E/F/H/I/J , A/C/0/D/E/F/H/I/J ).
right( A/B/C/D/0/F/H/I/J , A/B/C/D/F/0/H/I/J ).
right( A/B/C/D/E/F/H/0/J , A/B/C/D/E/F/H/J/0 ).
right( 0/B/C/D/E/F/H/I/J , B/0/C/D/E/F/H/I/J ).
right( A/B/C/0/E/F/H/I/J , A/B/C/E/0/F/H/I/J ).
right( A/B/C/D/E/F/0/I/J , A/B/C/D/E/F/I/0/J ).
down( A/B/C/0/E/F/H/I/J , A/B/C/H/E/F/0/I/J ).
down( A/B/C/D/0/F/H/I/J , A/B/C/D/I/F/H/0/J ).
down( A/B/C/D/E/0/H/I/J , A/B/C/D/E/J/H/I/0 ).
down( 0/B/C/D/E/F/H/I/J , D/B/C/0/E/F/H/I/J ).
down( A/0/C/D/E/F/H/I/J , A/E/C/D/0/F/H/I/J ).
down( A/B/0/D/E/F/H/I/J , A/B/F/D/E/0/H/I/J ).
%%% the heuristic function
h_function(Puzz,H) :- p_fcn(Puzz,P),
s_fcn(Puzz,S),
H is P + 3*S.
%%% the move
move(P,C,left) :- left(P,C).
move(P,C,up) :- up(P,C).
move(P,C,right) :- right(P,C).
move(P,C,down) :- down(P,C).
%%% the Manhattan distance function
p_fcn(A/B/C/D/E/F/G/H/I, P) :-
a(A,Pa), b(B,Pb), c(C,Pc),
d(D,Pd), e(E,Pe), f(F,Pf),
g(G,Pg), h(H,Ph), i(I,Pi),
P is Pa+Pb+Pc+Pd+Pe+Pf+Pg+Ph+Pg+Pi.
a(0,0). a(1,0). a(2,1). a(3,2). a(4,3). a(5,4). a(6,3). a(7,2). a(8,1).
b(0,0). b(1,1). b(2,0). b(3,1). b(4,2). b(5,3). b(6,2). b(7,3). b(8,2).
c(0,0). c(1,2). c(2,1). c(3,0). c(4,1). c(5,2). c(6,3). c(7,4). c(8,3).
d(0,0). d(1,1). d(2,2). d(3,3). d(4,2). d(5,3). d(6,2). d(7,2). d(8,0).
e(0,0). e(1,2). e(2,1). e(3,2). e(4,1). e(5,2). e(6,1). e(7,2). e(8,1).
f(0,0). f(1,3). f(2,2). f(3,1). f(4,0). f(5,1). f(6,2). f(7,3). f(8,2).
g(0,0). g(1,2). g(2,3). g(3,4). g(4,3). g(5,2). g(6,2). g(7,0). g(8,1).
h(0,0). h(1,3). h(2,3). h(3,3). h(4,2). h(5,1). h(6,0). h(7,1). h(8,2).
i(0,0). i(1,4). i(2,3). i(3,2). i(4,1). i(5,0). i(6,1). i(7,2). i(8,3).
%%% the out-of-cycle function
s_fcn(A/B/C/D/E/F/G/H/I, S) :-
s_aux(A,B,S1), s_aux(B,C,S2), s_aux(C,F,S3),
s_aux(F,I,S4), s_aux(I,H,S5), s_aux(H,G,S6),
s_aux(G,D,S7), s_aux(D,A,S8), s_aux(E,S9),
S is S1+S2+S3+S4+S5+S6+S7+S8+S9.
s_aux(0,0) :- !.
s_aux(_,1).
s_aux(X,Y,0) :- Y is X+1, !.
s_aux(8,1,0) :- !.
s_aux(_,_,2).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%% 8-puzzle animation -- using VT100 character graphics
%%%
%%%
%%%
puzzle(P) :- solve(P,S),
animate(P,S),
message.
animate(P,S) :- initialize(P),
cursor(1,2), write(S),
cursor(1,22), write('Hit ENTER to step solver.'),
get0(_X),
play_back(S).
:- dynamic location/3. %%% So that location of a tile
%%% can be retracted/asserted.
%%% Location(s) asserted and retracted
%%% by puzzle animator below
initialize(A/B/C/D/E/F/H/I/J) :-
cls,
retractall(location(_,_,_)),
assert(location(A,20,5)),
assert(location(B,30,5)),
assert(location(C,40,5)),
assert(location(F,40,10)),
assert(location(J,40,15)),
assert(location(I,30,15)),
assert(location(H,20,15)),
assert(location(D,20,10)),
assert(location(E,30,10)), draw_all.
draw_all :- draw(1), draw(2), draw(3), draw(4),
draw(5), draw(6), draw(7), draw(8).
%%% play_back([left,right,up,...]).
play_back([M|R]) :- call(M), get0(_X), play_back(R).
play_back([]) :- cursor(1,24). %%% Put cursor out of the way
message :- nl,nl,
write(' ********************************************'), nl,
write(' * Enter 8-puzzle goals in the form ... *'), nl,
write(' * ?- puzzle(0/8/1/2/4/3/7/6/5). *'), nl,
write(' * Enter goal ''message'' to reread this. *'), nl,
write(' ********************************************'), nl, nl.
cursor(X,Y) :- put(27), put(91), %%% ESC [
write(Y),
put(59), %%% ;
write(X),
put(72). %%% M
%%% clear the screen, quickly
cls :- put(27), put("["), put("2"), put("J").
%%% video attributes -- bold and blink not working
plain :- put(27), put("["), put("0"), put("m").
reverse_video :- put(27), put("["), put("7"), put("m").
%%% Tile objects, character map(s)
%%% Each tile should be drawn using the character map,
%%% drawn at 'location', which is asserted and retracted
%%% by 'playback'.
character_map(N, [ [' ',' ',' ',' ',' ',' ',' '],
[' ',' ',' ', N ,' ',' ',' '],
[' ',' ',' ',' ',' ',' ',' '] ]).
%%% move empty tile (spot) to the left
left :- retract(location(0,X0,Y0)),
Xnew is X0 - 10,
location(Tile,Xnew,Y0),
assert(location(0,Xnew,Y0)),
right(Tile),right(Tile),right(Tile),
right(Tile),right(Tile),
right(Tile),right(Tile),right(Tile),
right(Tile),right(Tile).
up :- retract(location(0,X0,Y0)),
Ynew is Y0 - 5,
location(Tile,X0,Ynew),
assert(location(0,X0,Ynew)),
down(Tile),down(Tile),down(Tile),down(Tile),down(Tile).
right :- retract(location(0,X0,Y0)),
Xnew is X0 + 10,
location(Tile,Xnew,Y0),
assert(location(0,Xnew,Y0)),
left(Tile),left(Tile),left(Tile),left(Tile),left(Tile),
left(Tile),left(Tile),left(Tile),left(Tile),left(Tile).
down :- retract(location(0,X0,Y0)),
Ynew is Y0 + 5,
location(Tile,X0,Ynew),
assert(location(0,X0,Ynew)),
up(Tile),up(Tile),up(Tile),up(Tile),up(Tile).
draw(Obj) :- reverse_video, character_map(Obj,M),
location(Obj,X,Y),
draw(X,Y,M), plain.
%%% hide tile
hide(Obj) :- character_map(Obj,M),
location(Obj,X,Y),
hide(X,Y,M).
hide(_,_,[]).
hide(X,Y,[R|G]) :- hide_row(X,Y,R),
Y1 is Y + 1,
hide(X,Y1,G).
hide_row(_,_,[]).
hide_row(X,Y,[_|R]) :- cursor(X,Y),
write(' '),
X1 is X + 1,
hide_row(X1,Y,R).
%%% draw tile
draw(_,_,[]).
draw(X,Y,[R|G]) :- draw_row(X,Y,R),
Y1 is Y + 1,
draw(X,Y1,G).
draw_row(_,_,[]).
draw_row(X,Y,[P|R]) :- cursor(X,Y),
write(P),
X1 is X + 1,
draw_row(X1,Y,R).
%%% Move an Object up
up(Obj) :- hide(Obj),
retract(location(Obj,X,Y)),
Y1 is Y - 1,
assert(location(Obj,X,Y1)),
draw(Obj).
down(Obj) :- hide(Obj),
retract(location(Obj,X,Y)),
Y1 is Y + 1,
assert(location(Obj,X,Y1)),
draw(Obj).
left(Obj) :- hide(Obj),
retract(location(Obj,X,Y)),
X1 is X - 1,
assert(location(Obj,X1,Y)),
draw(Obj).
right(Obj) :- hide(Obj),
retract(location(Obj,X,Y)),
X1 is X + 1,
assert(location(Obj,X1,Y)),
draw(Obj).
:- message.
% ?- solve(0/8/1/2/4/3/7/6/5, S).