def parse_f(l: List[Union[int, str]]) -> Node:
str_to_unop = {
"+": operations.identity,
"-": operations.negate,
}
if l[0] in str_to_unop:
op = l.pop(0)
return UnaryOp(str_to_unop[op], parse_f(l))
return parse_p(l)
def stack_to_tree(s: List[Union[int, str]]) -> Node:
top = s.pop()
if type(top) is int:
return Constant(top)
top = cast(str, top)
if top == "@":
rhs = stack_to_tree(s)
return UnaryOp(operations.negate, rhs)
rhs = stack_to_tree(s)
lhs = stack_to_tree(s)
return BinOp(operations.STR_TO_BIN[top], lhs, rhs)
def queue_to_tree(q: List[Union[int, str]]) -> Node:
top = q.pop(0)
if type(top) is int:
return Constant(top)
top = cast(str, top)
if top == "@":
rhs = queue_to_tree(q)
return UnaryOp(operations.negate, rhs)
lhs = queue_to_tree(q)
rhs = queue_to_tree(q)
return BinOp(operations.STR_TO_BIN[top], lhs, rhs)
def visit_unaryop(self, b: UnaryOp) -> None:
rhs_val = self.visit_and_get_value(b.rhs)
self.value = b.op(rhs_val)
def test_evaluate_unaryop_negate(vis):
op = UnaryOp(operations.negate, Constant(-42))
assert vis.visit_and_get_value(op) == 42
def test_evaluate_unaryop_identity(vis):
op = UnaryOp(operations.identity, Constant(42))
assert vis.visit_and_get_value(op) == 42
def test_parse_doubly_negated_constant():
assert parse_postfix("42@@") == UnaryOp(
operations.negate, UnaryOp(operations.negate, Constant(42)))
def test_parse_doubly_negated_constant():
assert parse_prefix("@@42") == UnaryOp(
operations.negate, UnaryOp(operations.negate, Constant(42)))