Grammar parsing code

Python code posted by Andy Norris
created at 01 Dec 19:34, updated at 02 Dec 13:17

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def parse(element,text):
  tokens = text.split()
  tokens.reverse()
  return rec_parse(element,tokens)

def rec_parse(element,tokens):
  for path in grammar[element]:
    elements = [element]
    item = None
    valid = True
    for word in path:
      if tokens[-1] == word:
        item = tokens.pop()
      elif word in grammar:
        item = rec_parse(word,tokens)
      if item != None:ss
        elements.append(item)
      else:
        valid = False
        break
    if valid:
      return elements
  return None

def parse_s(text):
  return parse('S', text)
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