abydos/phonetic/_metaphone.py
# Copyright 2014-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Abydos is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Abydos. If not, see <http://www.gnu.org/licenses/>.
"""abydos.phonetic._metaphone.
Metaphone
"""
from ._phonetic import _Phonetic
__all__ = ['Metaphone']
class Metaphone(_Phonetic):
"""Metaphone.
Based on Lawrence Philips' Pick BASIC code from 1990 :cite:`Philips:1990`,
as described in :cite:`Philips:1990b`.
This incorporates some corrections to the above code, particularly
some of those suggested by Michael Kuhn in :cite:`Kuhn:1995`.
.. versionadded:: 0.3.6
"""
_frontv = {'E', 'I', 'Y'}
_varson = {'C', 'G', 'P', 'S', 'T'}
def __init__(self, max_length: int = -1) -> None:
"""Initialize AlphaSIS instance.
Parameters
----------
max_length : int
The maximum length of the returned Metaphone code (defaults to 64,
but in Philips' original implementation this was 4)
.. versionadded:: 0.4.0
"""
# Require a max_length of at least 4
if max_length != -1:
self._max_length = max(4, max_length)
else:
self._max_length = 64
def encode(self, word: str) -> str:
"""Return the Metaphone code for a word.
Based on Lawrence Philips' Pick BASIC code from 1990
:cite:`Philips:1990`, as described in :cite:`Philips:1990b`.
This incorporates some corrections to the above code, particularly
some of those suggested by Michael Kuhn in :cite:`Kuhn:1995`.
Parameters
----------
word : str
The word to transform
Returns
-------
str
The Metaphone value
Examples
--------
>>> pe = Metaphone()
>>> pe.encode('Christopher')
'KRSTFR'
>>> pe.encode('Niall')
'NL'
>>> pe.encode('Smith')
'SM0'
>>> pe.encode('Schmidt')
'SKMTT'
.. versionadded:: 0.1.0
.. versionchanged:: 0.3.6
Encapsulated in class
"""
# As in variable sound--those modified by adding an "h"
ename = ''.join(c for c in word.upper() if c.isalnum())
# Delete non-alphanumeric characters and make all caps
if not ename:
return ''
if ename[0:2] in {'PN', 'AE', 'KN', 'GN', 'WR'}:
ename = ename[1:]
elif ename[0] == 'X':
ename = 'S' + ename[1:]
elif ename[0:2] == 'WH':
ename = 'W' + ename[2:]
# Convert to metaphone
elen = len(ename) - 1
metaph = ''
for i in range(len(ename)):
if len(metaph) >= self._max_length:
break
if (
ename[i] not in {'G', 'T'}
and i > 0
and ename[i - 1] == ename[i]
):
continue
if ename[i] in self._uc_v_set and i == 0:
metaph = ename[i]
elif ename[i] == 'B':
if i != elen or ename[i - 1] != 'M':
metaph += ename[i]
elif ename[i] == 'C':
if not (
i > 0
and ename[i - 1] == 'S'
and ename[i + 1 : i + 2] in self._frontv
):
if ename[i + 1 : i + 3] == 'IA':
metaph += 'X'
elif ename[i + 1 : i + 2] in self._frontv:
metaph += 'S'
elif i > 0 and ename[i - 1 : i + 2] == 'SCH':
metaph += 'K'
elif ename[i + 1 : i + 2] == 'H':
if (
i == 0
and i + 1 < elen
and ename[i + 2 : i + 3] not in self._uc_v_set
):
metaph += 'K'
else:
metaph += 'X'
else:
metaph += 'K'
elif ename[i] == 'D':
if (
ename[i + 1 : i + 2] == 'G'
and ename[i + 2 : i + 3] in self._frontv
):
metaph += 'J'
else:
metaph += 'T'
elif ename[i] == 'G':
if ename[i + 1 : i + 2] == 'H' and not (
i + 1 == elen or ename[i + 2 : i + 3] not in self._uc_v_set
):
continue
elif i > 0 and (
(i + 1 == elen and ename[i + 1] == 'N')
or (i + 3 == elen and ename[i + 1 : i + 4] == 'NED')
):
continue
elif (
i - 1 > 0
and i + 1 <= elen
and ename[i - 1] == 'D'
and ename[i + 1] in self._frontv
):
continue
elif ename[i + 1 : i + 2] == 'G':
continue
elif ename[i + 1 : i + 2] in self._frontv:
if i == 0 or ename[i - 1] != 'G':
metaph += 'J'
else:
metaph += 'K'
else:
metaph += 'K'
elif ename[i] == 'H':
if (
i > 0
and ename[i - 1] in self._uc_v_set
and ename[i + 1 : i + 2] not in self._uc_v_set
):
continue
elif i > 0 and ename[i - 1] in self._varson:
continue
else:
metaph += 'H'
elif ename[i] in {'F', 'J', 'L', 'M', 'N', 'R'}:
metaph += ename[i]
elif ename[i] == 'K':
if i > 0 and ename[i - 1] == 'C':
continue
else:
metaph += 'K'
elif ename[i] == 'P':
if ename[i + 1 : i + 2] == 'H':
metaph += 'F'
else:
metaph += 'P'
elif ename[i] == 'Q':
metaph += 'K'
elif ename[i] == 'S':
if (
i > 0
and i + 2 <= elen
and ename[i + 1] == 'I'
and ename[i + 2] in 'OA'
):
metaph += 'X'
elif ename[i + 1 : i + 2] == 'H':
metaph += 'X'
else:
metaph += 'S'
elif ename[i] == 'T':
if (
i > 0
and i + 2 <= elen
and ename[i + 1] == 'I'
and ename[i + 2] in {'A', 'O'}
):
metaph += 'X'
elif ename[i + 1 : i + 2] == 'H':
metaph += '0'
elif ename[i + 1 : i + 3] != 'CH':
if ename[i - 1 : i] != 'T':
metaph += 'T'
elif ename[i] == 'V':
metaph += 'F'
elif ename[i] in 'WY':
if ename[i + 1 : i + 2] in self._uc_v_set:
metaph += ename[i]
elif ename[i] == 'X':
metaph += 'KS'
elif ename[i] == 'Z':
metaph += 'S'
return metaph
if __name__ == '__main__':
import doctest
doctest.testmod()