def test_peek(self):
for length in range(10):
input_ = ''.join([choice(printable) for _ in range(length)])
input_stream = InputStream(input_)
for i in range(length):
self.assertEqual(input_[i], input_stream.peek())
input_stream.next()
for i in range(length, 2 * length + 1):
self.assertEqual('', input_stream.peek())
class TokenStream:
def __init__(self, text):
self.input_stream = InputStream(text + '\n')
self.current = None
self.has_peeked = False
def _is_whitespace(self, char):
return char in ' \t'
def _is_digit(self, char):
return char.isdigit()
def _is_operator(self, char):
return char in operators
def _read_while(self, predicate_func):
_str = ""
while not self.input_stream.is_eof() and predicate_func(
self.input_stream.peek()):
_str += self.input_stream.next()
return _str
def _read_number(self):
number = self._read_while(self._is_digit)
return {'type': 'num', 'value': int(number)}
def _read_operator(self):
return {'type': 'op', 'value': self.input_stream.next()}
def _read_next(self):
_ = self._read_while(self._is_whitespace)
if self.input_stream.is_eof():
return None
char = self.input_stream.peek()
if self._is_digit(char):
return self._read_number()
if self._is_operator(char):
return self._read_operator()
self.input_stream.croak("Can't handle character: " + char)
self.input_stream.next()
return None
def next(self):
if self.has_peeked:
self.has_peeked = False
return self.current
self.current = self._read_next()
return self.current
def peek(self):
if self.has_peeked:
return self.current
self.current = self._read_next()
self.has_peeked = True
return self.current
def is_eof(self):
return self.peek() is None
def croak(self, msg):
self.input_stream.croak(msg)