From: Albert Fox (plqueiroz@hotmail.com)
Date: Sat 15 Apr 2000 - 17:45:19 MEST
How is the query for this program work ??
/* Problem Solving :- Water Jugs Problem */
initial_state(jugs,jugs(0,0)).
final_state(jugs(4,0)).
final_state(jugs(0,4)).
move(jugs(V1,V2),fill(1)).
move(jugs(V1,V2),fill(2)).
move(jugs(V1,V2),empty(1)).
move(jugs(V1,V2),empty(2)).
move(jugs(V1,V2),transfer(2,1)).
move(jugs(V1,V2),transfer(1,2)).
update(jugs(V1,V2),fill(1),jugs(C1,V2)) :- capacity(1,C1).
update(jugs(V1,V2),fill(2),jugs(V1,C2)) :- capacity(2,C2).
update(jugs(V1,V2),empty(1),jugs(0,V2)).
update(jugs(V1,V2),empty(2),jugs(V1,0)).
update(jugs(V1,V2),transfer(2,1),jugs(W1,W2)) :-
capacity(1,C1),
Liquid is V1 + V2,
Excess is Liquid - C1,
adjust(Liquid,Excess,W1,W2).
update(jugs(V1,V2),transfer(1,2),jugs(W1,W2)) :-
capacity(2,C2),
Liquid is V1 + V2,
Excess is Liquid - C2,
adjust(Liquid,Excess,W2,W1).
adjust(Liquid, Excess,Liquid,0) :- Excess =< 0.
adjust(Liquid,Excess,V,Excess) :- Excess > 0, V is Liquid - Excess.
legal(jugs(V1,V2)).
capacity(1,8).
capacity(2,5).
% Program 20.3 Solving the water jugs problem
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