# Copyright 2018-2020 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.distance._sift4_simplest.
Sift4 Simplest approximate string distance
"""
from deprecation import deprecated
from ._sift4 import Sift4
from .. import __version__
__all__ = ['Sift4Simplest', 'sift4_simplest']
[docs]class Sift4Simplest(Sift4):
"""Sift4 Simplest version.
This is an approximation of edit distance, described in
:cite:`Zackwehdex:2014`.
.. versionadded:: 0.3.6
"""
def __init__(self, max_offset=5, **kwargs):
"""Initialize Sift4Simplest instance.
Parameters
----------
max_offset : int
The number of characters to search for matching letters
**kwargs
Arbitrary keyword arguments
.. versionadded:: 0.4.0
"""
super(Sift4Simplest, self).__init__(**kwargs)
self._max_offset = max_offset
[docs] def dist_abs(self, src, tar):
"""Return the "simplest" Sift4 distance between two terms.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
Returns
-------
int
The Sift4 distance according to the simplest formula
Examples
--------
>>> cmp = Sift4Simplest()
>>> cmp.dist_abs('cat', 'hat')
1
>>> cmp.dist_abs('Niall', 'Neil')
2
>>> cmp.dist_abs('Colin', 'Cuilen')
3
>>> cmp.dist_abs('ATCG', 'TAGC')
2
.. versionadded:: 0.3.0
.. versionchanged:: 0.3.6
Encapsulated in class
"""
if not src:
return len(tar)
if not tar:
return len(src)
src_len = len(src)
tar_len = len(tar)
src_cur = 0
tar_cur = 0
lcss = 0
local_cs = 0
while (src_cur < src_len) and (tar_cur < tar_len):
if src[src_cur] == tar[tar_cur]:
local_cs += 1
else:
lcss += local_cs
local_cs = 0
if src_cur != tar_cur:
src_cur = tar_cur = max(src_cur, tar_cur)
for i in range(self._max_offset):
if not (
(src_cur + i < src_len) or (tar_cur + i < tar_len)
):
break
if (
(src_cur + i < src_len)
and (tar_cur < tar_len)
and (src[src_cur + i] == tar[tar_cur])
):
src_cur += i
local_cs += 1
break
if (
(tar_cur + i < tar_len)
and (src_cur < src_len)
and (src[src_cur] == tar[tar_cur + i])
):
tar_cur += i
local_cs += 1
break
src_cur += 1
tar_cur += 1
lcss += local_cs
return round(max(src_len, tar_len) - lcss)
[docs]@deprecated(
deprecated_in='0.4.0',
removed_in='0.6.0',
current_version=__version__,
details='Use the Sift4Simplest.dist_abs method instead.',
)
def sift4_simplest(src, tar, max_offset=5):
"""Return the "simplest" Sift4 distance between two terms.
This is a wrapper for :py:meth:`Sift4Simplest.dist_abs`.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
max_offset : int
The number of characters to search for matching letters
Returns
-------
int
The Sift4 distance according to the simplest formula
Examples
--------
>>> sift4_simplest('cat', 'hat')
1
>>> sift4_simplest('Niall', 'Neil')
2
>>> sift4_simplest('Colin', 'Cuilen')
3
>>> sift4_simplest('ATCG', 'TAGC')
2
.. versionadded:: 0.3.0
"""
return Sift4Simplest(max_offset).dist_abs(src, tar)
if __name__ == '__main__':
import doctest
doctest.testmod()