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class Parser(object):
def __init__(self, tokens):
self.tokens = tokens
self.i = 0
def exhausted(self):
return self.i >= len(self.tokens)
def peek(self, n=0):
return self.tokens[self.i + n]
def advance(self):
if not self.exhausted():
self.i += 1
return self.peek(n=-1)
def match(self, xs):
if self.peek() in xs:
self.advance()
return True
return False
def test(self, predicate):
return predicate(self.tokens, self.i)
def expect(self, predicate):
if self.exhausted():
raise Exception("Unexpected EOL")
if predicate(self.peek()):
return self.advance()
raise Exception("Unexpected token: \"{}\"".format(self.peek()))
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