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Python

5 years ago
# Natural Language Toolkit: Combinatory Categorial Grammar
#
# Copyright (C) 2001-2019 NLTK Project
# Author: Tanin Na Nakorn (@tanin)
# URL: <http://nltk.org/>
# For license information, see LICENSE.TXT
"""
Helper functions for CCG semantics computation
"""
from nltk.sem.logic import *
def compute_type_raised_semantics(semantics):
core = semantics
parent = None
while isinstance(core, LambdaExpression):
parent = core
core = core.term
var = Variable("F")
while var in core.free():
var = unique_variable(pattern=var)
core = ApplicationExpression(FunctionVariableExpression(var), core)
if parent is not None:
parent.term = core
else:
semantics = core
return LambdaExpression(var, semantics)
def compute_function_semantics(function, argument):
return ApplicationExpression(function, argument).simplify()
def compute_composition_semantics(function, argument):
assert isinstance(argument, LambdaExpression), (
"`" + str(argument) + "` must be a lambda expression"
)
return LambdaExpression(
argument.variable, ApplicationExpression(function, argument.term).simplify()
)
def compute_substitution_semantics(function, argument):
assert isinstance(function, LambdaExpression) and isinstance(
function.term, LambdaExpression
), ("`" + str(function) + "` must be a lambda expression with 2 arguments")
assert isinstance(argument, LambdaExpression), (
"`" + str(argument) + "` must be a lambda expression"
)
new_argument = ApplicationExpression(
argument, VariableExpression(function.variable)
).simplify()
new_term = ApplicationExpression(function.term, new_argument).simplify()
return LambdaExpression(function.variable, new_term)