text: # Natural Language Toolkit: Cooper storage for Quantifier Ambiguity
  #
  # Copyright (C) 2001-2012 NLTK Project
  # Author: Ewan Klein <ewan@inf.ed.ac.uk>
  # URL: <http://www.nltk.org/>
  # For license information, see LICENSE.TXT
  
  from __future__ import print_function
  from logic import LambdaExpression, ApplicationExpression, Variable, LogicParser
  from nltk.parse import load_parser
  from nltk.parse.featurechart import InstantiateVarsChart
  
  class CooperStore(object):
      """
      A container for handling quantifier ambiguity via Cooper storage.
      """
      def __init__(self, featstruct):
          """
          :param featstruct: The value of the ``sem`` node in a tree from
              ``parse_with_bindops()``
          :type featstruct: FeatStruct (with features ``core`` and ``store``)
  
          """
          self.featstruct = featstruct
          self.readings = []
          try:
              self.core = featstruct['CORE']
              self.store = featstruct['STORE']
          except KeyError:
              print("%s is not a Cooper storage structure" % featstruct)
  
      def _permute(self, lst):
          """
          :return: An iterator over the permutations of the input list
          :type lst: list
          :rtype: iter
          """
          remove = lambda lst0, index: lst0[:index] + lst0[index+1:]
          if lst:
              for index, x in enumerate(lst):
                  for y in self._permute(remove(lst, index)):
                      yield (x,)+y
          else: yield ()
  
      def s_retrieve(self, trace=False):
          """
          Carry out S-Retrieval of binding operators in store. If hack=True,
          serialize the bindop and core as strings and reparse. Ugh.
  
          Each permutation of the store (i.e. list of binding operators) is
          taken to be a possible scoping of quantifiers. We iterate through the
          binding operators in each permutation, and successively apply them to
          the current term, starting with the core semantic representation,
          working from the inside out.
  
          Binding operators are of the form::
  
               bo(\P.all x.(man(x) -> P(x)),z1)
          """
          for perm, store_perm in enumerate(self._permute(self.store)):
              if trace:
                  print("Permutation %s" % (perm+1))
              term = self.core
              for bindop in store_perm:
                  # we just want the arguments that are wrapped by the 'bo' predicate
                  quant, varex = tuple(bindop.args)
                  # use var to make an abstraction over the current term and then
                  # apply the quantifier to it
                  term = ApplicationExpression(quant, LambdaExpression(varex.variable, term))
                  if trace:
                      print("  ", term)
                  term = term.simplify()
              self.readings.append(term)
  
  
  def parse_with_bindops(sentence, grammar=None, trace=0):
      """
      Use a grammar with Binding Operators to parse a sentence.
      """
      if not grammar:
          grammar = 'grammars/book_grammars/storage.fcfg'
      parser = load_parser(grammar, trace=trace, chart_class=InstantiateVarsChart)
      # Parse the sentence.
      tokens = sentence.split()
      return parser.nbest_parse(tokens)
  
  
  def demo():
      from nltk.sem import cooper_storage as cs
      sentence = "every girl chases a dog"
      #sentence = "a man gives a bone to every dog"
      print()
      print("Analyis of sentence '%s'" % sentence)
      print("=" * 50)
      trees = cs.parse_with_bindops(sentence, trace=0)
      for tree in trees:
          semrep = cs.CooperStore(tree.node['SEM'])
          print()
          print("Binding operators:")
          print("-" * 15)
          for s in semrep.store:
              print(s)
          print()
          print("Core:")
          print("-" * 15)
          print(semrep.core)
          print()
          print("S-Retrieval:")
          print("-" * 15)
          semrep.s_retrieve(trace=True)
          print("Readings:")
          print("-" * 15)
  
          for i, reading in enumerate(semrep.readings):
              print("%s: %s" % (i+1, reading))
  
  if __name__ == '__main__':
      demo()
  