# Source code for abydos.distance._marking_metric

# Copyright 2019-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# 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._marking_metric.

Ehrenfeucht & Haussler's marking metric
"""

from math import log2

from ._marking import Marking

__all__ = ['MarkingMetric']

[docs]class MarkingMetric(Marking):
r"""Ehrenfeucht & Haussler's marking metric.

This metric :cite:Ehrenfeucht:1988 is the base 2 logarithm of the product
of the marking distances between each term plus 1 computed in both orders.
For strings x and y, this is:

.. math::

dist_{MarkingMetric}(x, y) =
log_2((diff(x, y)+1)(diff(y, x)+1))

The function diff is Ehrenfeucht & Haussler's marking distance
:class:Marking.

"""

def __init__(self, **kwargs):
"""Initialize MarkingMetric instance.

Parameters
----------
**kwargs
Arbitrary keyword arguments

"""
super(MarkingMetric, self).__init__(**kwargs)

[docs]    def dist_abs(self, src, tar):
"""Return the marking distance of two strings.

Parameters
----------
src : str
Source string (or QGrams/Counter objects) for comparison
tar : str
Target string (or QGrams/Counter objects) for comparison

Returns
-------
int
marking distance

Examples
--------
>>> cmp = MarkingMetric()
>>> cmp.dist_abs('cat', 'hat')
2.0
>>> cmp.dist_abs('Niall', 'Neil')
3.584962500721156
>>> cmp.dist_abs('aluminum', 'Catalan')
4.584962500721156
>>> cmp.dist_abs('ATCG', 'TAGC')
3.169925001442312
>>> cmp.dist_abs('cbaabdcb', 'abcba')
2.584962500721156

"""
diff1 = super(MarkingMetric, self).dist_abs(src, tar)
diff2 = super(MarkingMetric, self).dist_abs(tar, src)
return log2((diff1 + 1) * (diff2 + 1))

[docs]    def dist(self, src, tar):
"""Return the normalized marking distance of two strings.

Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison

Returns
-------
float
marking distance

Examples
--------
>>> cmp = Marking()
>>> cmp.dist('cat', 'hat')
0.3333333333333333
>>> cmp.dist('Niall', 'Neil')
0.6
>>> cmp.dist('aluminum', 'Catalan')
0.625
>>> cmp.dist('ATCG', 'TAGC')
0.5
>>> cmp.dist('cbaabdcb', 'abcba')
0.25