table_value

table_value(Table, Key, Value, L) :-
    semipure det_checkstack(L, 6),
    semipure var_type(Table, table_type, L),
    impure lua_newtable(L), % Memo set table
    impure push_var(Table, L),
    impure lua_pushboolean(L, yes),
    impure lua_rawset(L, -3), % Add the Table to the memo set table
    semipure Last = lua_toref(L, -1),
    impure lua_pop(L, 1).
    semipure table_value(Table, Key, Value, Last, L).

:- semipure pred table_value(var, value, value, ref, lua).
:- mode valid_table(in, out, out, in, in) is nondet.

table_value(Table, Key, Value, Last, L) :-
    impure push_var(Table, L)   % Table being iterated
    impure lua_pushref(L, Last),    % Last key
    impure lua_next(L, -2), % Pop the last key and push the next pair
    % The stack should now look like [Table, Key, Value]
    semipure lua_isnil(L, -2) ->    % Is there another pair?
        impure lua_pop(L, 3),   % Clear the stack
        fail            % There are no more pairs
    ;
        semipure Next =  lua_toref(L, -2),
        semipure Key = to_value(-2, L),
        semipure Value = to_value(-1, L),
        impure lua_pop(L, 3), % Clear the stack
    ;
        table_value(Table, Key, Value, Next, L).