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# Natural Language Toolkit: Combinatory Categorial Grammar
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#
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# Copyright (C) 2001-2020 NLTK Project
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# Author: Tanin Na Nakorn (@tanin)
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# URL: <http://nltk.org/>
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# For license information, see LICENSE.TXT
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"""
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Helper functions for CCG semantics computation
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"""
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from nltk.sem.logic import *
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def compute_type_raised_semantics(semantics):
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core = semantics
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parent = None
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while isinstance(core, LambdaExpression):
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parent = core
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core = core.term
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var = Variable("F")
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while var in core.free():
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var = unique_variable(pattern=var)
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core = ApplicationExpression(FunctionVariableExpression(var), core)
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if parent is not None:
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parent.term = core
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else:
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semantics = core
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return LambdaExpression(var, semantics)
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def compute_function_semantics(function, argument):
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return ApplicationExpression(function, argument).simplify()
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def compute_composition_semantics(function, argument):
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assert isinstance(argument, LambdaExpression), (
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"`" + str(argument) + "` must be a lambda expression"
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)
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return LambdaExpression(
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argument.variable, ApplicationExpression(function, argument.term).simplify()
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)
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def compute_substitution_semantics(function, argument):
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assert isinstance(function, LambdaExpression) and isinstance(
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function.term, LambdaExpression
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), ("`" + str(function) + "` must be a lambda expression with 2 arguments")
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assert isinstance(argument, LambdaExpression), (
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"`" + str(argument) + "` must be a lambda expression"
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)
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new_argument = ApplicationExpression(
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argument, VariableExpression(function.variable)
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).simplify()
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new_term = ApplicationExpression(function.term, new_argument).simplify()
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return LambdaExpression(function.variable, new_term)
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