def _consumeNumber(self,
stream: StringStream) -> Optional[NumberExpression]:
if not self._can_consumeDigit(stream):
return None
token = stream.next()
while self._can_consumeDigit(stream):
token += stream.next()
return token
def parse(self, stream: StringStream) -> Optional[NumberExpression]:
if not self.can_consume(stream):
return None
token: str = stream.peek()
if token.isspace():
stream.next()
return self.parse(stream)
isNegative = self._isNegativeSign(token)
if isNegative:
stream.next()
numberToken = self._consumeNumber(stream)
return NumberExpression(numberToken, isNegative)
def parse(self, stream: StringStream) -> Optional[Expression]:
while stream.has_chars() and not stream.peek() == ')':
if not self._can_consume(stream):
stream.next()
continue
if self._consume_number(stream):
continue
self._consume_operator(stream)
if stream.peek() == '(':
stream.next()
self._evaluate_bracket_expression(stream)
return self._tree.create_expression()
def parse(self, stream: StringStream) -> Optional[Operator]:
if not self.can_consume(stream):
return None
token: str = stream.next()
if token == '+':
return AddOperator()
elif token == '-':
return SubtractOperator()
elif token == '*':
return MultiplyOperator()
elif token == '/':
return DivideOperator()
elif token.isspace():
return self.parse(stream)