% move( State1, Move, State2): making Move in State1 results in State2;
% a state is represented by a structure:
% state( MonkeyHorizontal, MonkeyVertical, BoxPosition, HasBanana)

move( state( middle, onbox, middle, hasnot), % Before move
grasp,  % Grasp banana
state( middle, onbox, middle, has) ). % After move

move( state( P, onfloor, P, H),
climb, %Climb box
state( P, onbox, P, H) ).

move( state( P1, onfloor, P1, H),
push( P1, P2),  % Push box from P1 to P2
state( P2, onfloor, P2, H) ).

move( state( P1, onfloor, B, H),
walk( P1, P2),  % Walk from P1 to P2
state( P2, onfloor, B, H) ).

canget( state( _, _, _, has) ). % can 1: Monkey already has it
canget( State1) :- % can 2: Do some work to get it
move( State1, Move, State2),  % Do something
canget( State2), % Get it now
write(Move),nl. % report moves: will appear in reverse order