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class Parser(object):
def __init__(self, tokens):
self.tokens = tokens
self.i = 0
def prev(self):
return self.tokens[self.i - 1]
def curr(self):
return self.tokens[self.i]
def next(self):
return self.tokens[self.i + 1]
def consume(self):
if not self.exhausted():
self.i += 1
return self.prev()
def match(self, xs):
if not self.exhausted() and self.curr() in xs:
self.consume()
return True
return False
def expect(self, xs):
if not self.match(xs):
raise Exception("Expected token \"{}\" but received \"{}\"".format(xs, self.curr()))
return self.prev()
def expect_predicate(self, predicate):
if predicate(self.curr()):
return self.consume()
raise Exception("Expected token \"{}\" to pass predicate, but it did not".format(self.curr()))
def exhausted(self):
return self.i >= len(self.tokens)
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