def check_action(self, state: State, action: Action) -> bool:
"""
Check if an action should be allowed in this state.
The default implementation disallows actions that would create new facts
that don't mention any new variables.
Args:
state: The current state.
action: The action being applied.
Returns:
Whether that action should be allowed.
"""
for prop in action.preconditions:
if not state.is_fact(prop):
if all(state.has_variable(var) for var in prop.arguments):
# Don't allow creating new predicates without any new variables
return False
return True
def test_state():
state = State()
P = Variable.parse("P")
kitchen = Variable.parse("kitchen: r")
study = Variable.parse("study: r")
stove = Variable.parse("stove: o")
at_kitchen = Proposition.parse("at(P, kitchen: r)")
in_kitchen = Proposition.parse("in(stove: o, kitchen: r)")
at_study = Proposition.parse("at(P, study: r)")
assert not state.is_fact(at_kitchen)
assert not state.is_fact(in_kitchen)
assert not state.is_fact(at_study)
assert len(state.variables) == 0
assert len(state.variables_of_type("P")) == 0
assert len(state.variables_of_type("r")) == 0
assert len(state.variables_of_type("o")) == 0
state.add_fact(at_kitchen)
state.add_fact(in_kitchen)
assert state.is_fact(at_kitchen)
assert state.is_fact(in_kitchen)
assert not state.is_fact(at_study)
assert set(state.variables) == {P, kitchen, stove}
assert state.variables_of_type("P") == {P}
assert state.variables_of_type("r") == {kitchen}
assert state.variables_of_type("o") == {stove}
state.remove_fact(at_kitchen)
assert not state.is_fact(at_kitchen)
assert state.is_fact(in_kitchen)
assert not state.is_fact(at_study)
assert set(state.variables) == {kitchen, stove}
assert len(state.variables_of_type("P")) == 0
assert state.variables_of_type("r") == {kitchen}
assert state.variables_of_type("o") == {stove}
state.remove_fact(in_kitchen)
assert not state.is_fact(at_kitchen)
assert not state.is_fact(in_kitchen)
assert not state.is_fact(at_study)
assert len(state.variables) == 0
assert len(state.variables_of_type("P")) == 0
assert len(state.variables_of_type("r")) == 0
assert len(state.variables_of_type("o")) == 0
state.add_fact(at_study)
assert not state.is_fact(at_kitchen)
assert not state.is_fact(in_kitchen)
assert state.is_fact(at_study)
assert set(state.variables) == {P, study}
assert state.variables_of_type("P") == {P}
assert state.variables_of_type("r") == {study}
assert len(state.variables_of_type("o")) == 0