Water jug problem in Prolog best first search

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I failed to write a Prolog program using RBFS algorithm to solve a task - how to measure exactly 3 liters of water using 5-liter and 9-liter water jugs? I have a solution, but it does not use best-first search algorithm and works blindly (without heuristics). Can you please provide some pieces of code to apply RBFS algorithm to my task?

What I have tried:

Tried to use blind searching without heuristics
My code

volume(9,5).

program(A,B,W):-
    volume(VA,VB),
    A>=0,
    A=<VA,
    B>=0,
    B=<VB,
    change(A,B,[[A,B]],W),
    write1(W).
	
write1([]).
write1([X|L]):-
    writeln(X),
    write1(L).

element(A,B,W,W1):-
    not(member([A,B],W)),
    add1([A,B],W,W2),
    change(A,B,W2,W1).
              
change(3,_,W,W).
change(_,3,W,W).

change(A,B,W,W1):-
    volume(VA,_),
    B>0,
    C is VA-A,
    C>0,
    min(B,C,Min),
    A1 is A+Min,
    B1 is B-Min,
    element(A1,B1,W,W1).

change(A,B,W,W1):-
    volume(_,VB),
    A>0,
    C is VB-B,
    C>0,
    min(A,C,Min),
    B1 is B+Min,
    A1 is A-Min,
    element(A1,B1,W,W1).

change(A,B,W,W1):-
    volume(VA,_),
    A=VA,
    B>0,
    element(0,B,W,W1).

change(A,B,W,W1):-
    volume(_,VB),
    A>0,
    B=VB,
    element(A,0,W,W1).

change(A,B,W,W1):-
    volume(VA,_),
    A=0,
    element(VA,B,W,W1).

change(A,B,W,W1):-
    volume(_,VB),
    B=0,
    element(A,VB,W,W1).
    
min(A,B,A):- A=<B.
min(A,B,B):-A>B.

add(X,L,[X|L]). 

add1(X,[],[X]).
add1(X,[X1|L],[X1|L1]):-
    add1(X,L,L1).

Posted 23-Feb-21 10:50am

NickResh777

Updated 25-Feb-21 2:25am

PIEBALDconsult

v3

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Patrice T 23-Feb-21 19:17pm

Show your work

NickResh777 24-Feb-21 10:08am

I just updated my question and added my code

2 solutions

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Patrice T · Answer 1 · 2021-02-25T02:25:00

Quote:
I failed to write a Prolog program using RBFS algorithm to solve a task

For RBFS, you need a function to estimate which option is the most promising, but for this problem, I see no such obvious function.
So my approach would be an arbitrary function such as

A and B are the contains of both jugs
Func is the difference with target
Func= min(abs(A-3),abs(B-3))

OriginalGriff · Answer 2 · 2021-02-23T11:39:00

We are more than willing to help those that are stuck: but that doesn't mean that we are here to do it all for you! We can't do all the work, you are either getting paid for this, or it's part of your grades and it wouldn't be at all fair for us to do it all for you.

So we need you to do the work, and we will help you when you get stuck. That doesn't mean we will give you a step by step solution you can hand in!
Start by explaining where you are at the moment, and what the next step in the process is. Then tell us what you have tried to get that next step working, and what happened when you did.

If you are having problems getting started at all, then this may help: How to Write Code to Solve a Problem, A Beginner's Guide[^]

Water jug problem in Prolog best first search

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Water jug problem in Prolog best first search

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