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from story6.memo import memoize
class Parser:
def __init__(self, tokenizer):
self.tokenizer = tokenizer
self.memos = {}
def mark(self):
return self.tokenizer.mark()
def reset(self, pos):
self.tokenizer.reset(pos)
def show_rule(self, name, alts):
# alts is a list of lists of strings
vis = self.tokenizer.vis
if vis:
vis.show_rule(name, alts)
def show_index(self, alt_index, item_index, num_items=1):
vis = self.tokenizer.vis
if vis:
vis.show_index(alt_index, item_index, num_items)
return True
@memoize
def expect(self, arg):
token = self.tokenizer.peek_token()
if token.type == arg or token.string == arg:
return self.tokenizer.get_token()
return None
def loop(self, nonempty, func, *args):
mark = self.mark()
nodes = []
while node := func(*args) is not None:
nodes.append(node)
if len(nodes) >= nonempty:
return nodes
self.reset(mark)
return None
def lookahead(self, positive, func, *args):
mark = self.mark()
ok = func(*args) is not None
self.reset(mark)
return ok == positive
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