123 lines
3.8 KiB
Python
123 lines
3.8 KiB
Python
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#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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# Copyright 2014 California Institute of Technology. ALL RIGHTS RESERVED.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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# United States Government Sponsorship acknowledged. This software is subject to
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# U.S. export control laws and regulations and has been classified as 'EAR99 NLR'
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# (No [Export] License Required except when exporting to an embargoed country,
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# end user, or in support of a prohibited end use). By downloading this software,
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# the user agrees to comply with all applicable U.S. export laws and regulations.
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# The user has the responsibility to obtain export licenses, or other export
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# authority as may be required before exporting this software to any 'EAR99'
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# embargoed foreign country or citizen of those countries.
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#
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# Author: Eric Belz
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#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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"""Suported morphemes are affixes. The Affix ABC (and subclass of the list
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built-in) has two concrete subs:
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Prefix
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Suffix
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They know how to apply themselves, and they know what to do to Grammar
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as it traverses the IFT.
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"""
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## \namespace rdf.language.grammar.morpheme Key Changing Morphemes
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import abc
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## Abstract Base Class for Pre/Suf behavior
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class Affix(list):
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"""The Affix is an abstract base class.
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It implements the:
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descend/asend methods for traversing the IFT
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It is callable: Given a key, it will do what morphemes do and make
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as new key per the RDF spec.
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Sub classes use operator overloads to do their thing
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"""
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__metaclass__ = abc.ABCMeta
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## Descend the IFT-- add a null string to the affix list
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## \param None
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## \par Side Effects:
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## Append null string to Affix
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## \returns None
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def descend(self):
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"""append null string to self"""
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return self.append("")
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## Ascend the IFT-- pop the affix off and forget it
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## \param None
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## \par Side Effects:
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## Pops last affix off of Affix
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## \returns None
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def ascend(self):
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"""pop() from self"""
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return self.pop()
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## Call implements the construction of the affix (so IF you change the def
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## you change this 1 line of code.
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## \returns Sum of self- the complete affix
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def __call__(self):
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"""call implements the nest affix protocol: add 'em up"""
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return "".join(self)
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## strictly for safety
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def __add__(self, other):
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from rdf.language import errors
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raise (
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{True: errors.MorphemeExchangeError(
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"Cannot Pre/Ap-pend a Suf/Pre-fix"),
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False: TypeError("Can only add strings to this list sub")}[
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isinstance(other, basestring)
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]
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)
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__radd__ = __add__
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## Appears Before the stem:
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class Prefix(Affix):
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"""prefix + stem
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is the only allowed operator overload- it, by definition, must
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be prepended"""
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## prefix + stem (overides list concatenation)
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def __add__(self, stem):
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return self() + stem
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## Appears After the stem
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class Suffix(Affix):
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"""stem + suffix
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is the only allowed operator overload- it, by definition, must
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be appended"""
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## stem + prefix (overides list concatenation)
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def __radd__(self, stem):
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return stem + self()
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