Question

Getting an error:

ERROR: is/2: Arguments are not sufficiently instantiated

/*
*Go predicate
* Call as follows:
* ?- go(state(3,3,w),state(0,0,e)).
*/

go(Start,Goal) :-
   empty_stack(Empty_visited_stack),
   stack(Start,Empty_visited_stack,Visited_stack),
   path(Start,Goal,Visited_stack).

/*
* path predicates
*/

path(Goal,Goal,Visited_stack) :-
   write('Solution path is:' ), nl,
   write(Visited_stack).

path(State,Goal,Visited_stack) :-
   move(State,Next_state),
   not(member_stack(Next_state,Visited_stack)),
   stack(Next_state,Visited_stack,New_visited_stack),
   path(Next_state,Goal,New_visited_stack).

safe(M1,C1) :-
   (M1 =< C1; C1 = 0),
    M2 is 3-M1, C2 is 3-C1,
    (M2 =< C2; C2 = 0).

/*
* move predicates
*/

%move one monster from west to east
move(state(M1, H1, w), state(M2, H1,e)) :-
   M1 > 0,
   M2 is M1-1,
   safe(M2, H1).

%move two monster from west to east
move(state(M1, H1, w), state(M2,H1,e)) :-
   M1 > 1,
   M2 is M1-2,
   safe(M2, H1).

%move one human and one monster from west to east
move(state(M1,H1,w),state(M2, H2,e)) :-
   M1 > 0,
   H1 > 0,
   M2 is M1-1,
   H2 is H1-1,
   safe(M2, H2).

%move one human from west to east
move(state(M1,H1,w), state(M1,H2,e)) :-
   H1 > 0,
   H2 is H2-1,
   safe(M1,H2).

%move two humans from west to east
move(state(M1, H1, w), state(M1, H2, e)) :-
   H1 > 1,
   H2 is H1-2,
   safe(M1,H2).

%move one monster from east to west
move(state(M1, H1, e), state(M2, H1,w)) :-
   M1 < 3,
   M2 is M1 + 1,
   safe(M2, H1).

%move two monsters from east to west
move(state(M1, H1, e), state(M2,H1,w)) :-
   M1 < 2,
   M2 is M1 + 2,
   safe(M2,H1).

%move one monster and one human from east to west
move(state(M1, H1, e),state(M2, H2, w)) :-
   M1 < 3,
   H1 < 3,
   M2 is M1 +1,
   H2 is H1 +1,
   safe(M2, H2).

%move one human from east to west
move(state(M1, H1, e), state(M1,H2,w)) :-
   H1 < 3,
   H2 is H1+1,
   safe(M1,H2).

%move two humans from east to west
move(state(M1,H1,e), state(M1, H2,w)):-
   H1 < 2,
   H2 is H2 + 2,
   safe(M1,H2).

/*
* stack abstract data type
*/

member(X,[X|_]).
member(X,[_|T]) :- member(X,T).

empty_stack([]).
member_stack(E, S) :- member(E, S).
stack(E, S, [E|S]).

/*
* definition of writelist
*/

writelist([]) :- nl.
writelist([H|T]):-
   write(H),
   tab(1), /* "tab(n)" skips n spaces. */
   writelist(T).

It's the missionaries and cannibals problem in prolog, M for Missionary, H for Cannibals
Any help is highly appreciated!

Answer 1

* ?- go(state(3,3,w),state(0,0,e)).
*/

go(Start,Goal) :-
   empty_stack(Empty_visited_stack),
   stack(Start,Empty_visited_stack,Visited_stack),
   path(Start,Goal,Visited_stack).

/*
* path predicates
*/

path(Goal,Goal,Visited_stack) :-
   write('Solution path is:' ), nl,
   write(Visited_stack).

path(State,Goal,Visited_stack) :-
   move(State,Next_state),
   not(member_stack(Next_state,Visited_stack)),
   stack(Next_state,Visited_stack,New_visited_stack),
   path(Next_state,Goal,New_visited_stack).

safe(M1,C1) :-
   (M1 =< C1; C1 = 0),
    M2 is 3-M1, C2 is 3-C1,
    (M2 = C2; C2 = 0).

/*
* move predicates
*/

%move one monster from west to east
move(state(M1, H1, w), state(M2, H1,e)) :-
   M1 >= 0,
   M2 is M1-1,
   safe(M2, H1).

%move two monster from west to east
move(state(M1, H1, w), state(M2,H1,e)) :-
   M1 > 1,
   M2 is M1-2,
   safe(M2, H1).

%move one human and one monster from west to east
move(state(M1,H1,w),state(M2, H2,e)) :-
   M1 > 0,
   H1 > 0,
   M2 is M1-1,
   H2 is H1-1,
   safe(M2, H2).

%move one human from west to east
move(state(M1,H1,w), state(M1,H2,e)) :-
   H1 > 0,
   H2 is H2-1,
   safe(M1,H2).

%move two humans from west to east
move(state(M1, H1, w), state(M1, H2, e)) :-
   H1 > 1,
   H2 is H1-2,
   safe(M1,H2).

%move one monster from east to west
move(state(M1, H1, e), state(M2, H1,w)) :-
   M1 < 3,
   M2 is M1 + 1,
   safe(M2, H1).

%move two monsters from east to west
move(state(M1, H1, e), state(M2,H1,w)) :-
   M1 < 2,
   M2 is M1 - 2,
   safe(M2,H1).

%move one monster and one human from east to west
move(state(M1, H1, e),state(M2, H2, w)) :-
   M1 < 3,
   H1 < 3,
   M2 is M1 +1,
   H2 is H1 +1,
   safe(M2, H2).

%move one human from east to west
move(state(M1, H1, e), state(M1,H2,w)) :-
   H1 < 3,
   H2 is H1+1,
   safe(M1,H2).

%move two humans from east to west
move(state(M1,H1,e), state(M1, H2,w)):-
   H1 < 2,
   H2 is H2 - 2,
   safe(M1,H2).

/*
* stack abstract data type
*/

member(X,[X|_]).
member(X,[_|T]) :- member(X,T).

empty_stack([]).
member_stack(E, S) :- member(E, S).
stack(E, S, [E|S]).

/*
* definition of writelist
*/

writelist([]) :- nl.
writelist([H|T]):-
   write(H),
   tab(1), /* "tab(n)" skips n spaces. */
   writelist(T).