# -*- coding: utf-8 -*-
"""
Copyright Sylvain Bouveret, Yann Chevaleyre and François Durand
sylvain.bouveret@imag.fr, yann.chevaleyre@dauphine.fr, fradurand@gmail.com
This file is part of Whalrus.
Whalrus 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.
Whalrus 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 Whalrus. If not, see <http://www.gnu.org/licenses/>.
"""
import numbers
from whalrus.converters_ballot.converter_ballot import ConverterBallot
from whalrus.converters_ballot.converter_ballot_general import ConverterBallotGeneral
from whalrus.ballots.ballot_veto import BallotVeto
from whalrus.ballots.ballot_plurality import BallotPlurality
from whalrus.ballots.ballot_one_name import BallotOneName
from whalrus.ballots.ballot_levels import BallotLevels
from whalrus.ballots.ballot_order import BallotOrder
from whalrus.scales.scale import Scale
from whalrus.scales.scale_interval import ScaleInterval
from whalrus.scales.scale_from_list import ScaleFromList
from whalrus.scales.scale_from_set import ScaleFromSet
from whalrus.scales.scale_range import ScaleRange
from whalrus.scorers.scorer_borda import ScorerBorda
from whalrus.utils.utils import my_division
[docs]class ConverterBallotToLevelsInterval(ConverterBallot):
"""0
Default converter to a :class:`BallotLevels` using a :class:`ScaleInterval` (interval of real numbers).
Parameters
----------
scale : ScaleInterval
borda_unordered_give_points : bool
When converting a :class:`BallotOrder` that is not a :class:`BallotLevels`, we use Borda scores (normalized to
the interval [``scale.low``, ``scale.high``]. This parameter decides whether the unordered candidates of the
ballot give points to the ordered candidates. Cf. :class:`ScorerBorda`.
Examples
--------
Typical usages:
>>> converter = ConverterBallotToLevelsInterval()
>>> b = BallotLevels({'a': 1, 'b': .5}, candidates={'a', 'b', 'c'}, scale=ScaleInterval(-1, 1))
>>> converter(b).as_dict
{'a': 1, 'b': Fraction(3, 4)}
>>> b = BallotLevels({'a': 5, 'b': 4}, candidates={'a', 'b', 'c'}, scale=ScaleRange(0, 5))
>>> converter(b).as_dict
{'a': 1, 'b': Fraction(4, 5)}
>>> b = BallotLevels({'a': 3, 'b': 0}, candidates={'a', 'b', 'c'}, scale=ScaleFromSet({-1, 0, 3}))
>>> converter(b).as_dict
{'a': 1, 'b': Fraction(1, 4)}
>>> b = BallotLevels({'a': 'Excellent', 'b': 'Very Good'}, candidates={'a', 'b', 'c'},
... scale=ScaleFromList(['Bad', 'Medium', 'Good', 'Very Good', 'Excellent']))
>>> converter(b).as_dict
{'a': 1, 'b': Fraction(3, 4)}
>>> converter(BallotOneName('a', candidates={'a', 'b', 'c'})).as_dict
{'a': 1, 'b': 0, 'c': 0}
>>> converter(BallotPlurality('a', candidates={'a', 'b', 'c'})).as_dict
{'a': 1, 'b': 0, 'c': 0}
>>> converter(BallotVeto('a', candidates={'a', 'b', 'c'})).as_dict
{'a': 0, 'b': 1, 'c': 1}
>>> converter('a > b > c').as_dict
{'a': 1, 'b': Fraction(1, 2), 'c': 0}
Options for converting ordered ballots:
>>> b = BallotOrder('a > b > c', candidates={'a', 'b', 'c', 'd', 'e'})
>>> ConverterBallotToLevelsInterval(borda_unordered_give_points=False)(b).as_dict
{'a': 1, 'b': Fraction(1, 2), 'c': 0}
>>> ConverterBallotToLevelsInterval(borda_unordered_give_points=True)(b).as_dict
{'a': 1, 'b': Fraction(3, 4), 'c': Fraction(1, 2)}
"""
def __init__(self, scale: Scale = ScaleInterval(0, 1), borda_unordered_give_points: bool = True):
self.scale = scale
self.low = scale.low
self.high = scale.high
self.borda_unordered_give_points = borda_unordered_give_points
def __call__(self, x: object, candidates: set=None) -> BallotLevels:
x = ConverterBallotGeneral()(x, candidates=None)
if isinstance(x, BallotVeto):
if x.candidate is None:
return BallotLevels(dict(), candidates=x.candidates, scale=self.scale).restrict(candidates=candidates)
return BallotLevels({c: self.low if c == x.candidate else self.high for c in x.candidates},
candidates=x.candidates, scale=self.scale).restrict(candidates=candidates)
if isinstance(x, BallotOneName): # Including Plurality
if x.candidate is None:
return BallotLevels(dict(), candidates=x.candidates, scale=self.scale).restrict(candidates=candidates)
return BallotLevels({c: self.high if c == x.candidate else self.low for c in x.candidates},
candidates=x.candidates, scale=self.scale).restrict(candidates=candidates)
if isinstance(x, BallotLevels):
if not x.scale.is_bounded:
if all([isinstance(v, numbers.Number) for v in x.values()]):
x_min, x_max = min(x.values()), max(x.values())
if x_min >= self.low and x_max <= self.high:
return BallotLevels(
x.as_dict, candidates=x.candidates,
scale=ScaleInterval(low=self.low, high=self.high)).restrict(candidates=candidates)
else:
x = BallotLevels(x.as_dict, candidates=x.candidates,
scale=ScaleInterval(low=min(x.values()), high=max(x.values())))
else:
x = BallotLevels(x.as_dict, candidates=x.candidates, scale=ScaleFromSet(set(x.values())))
try: # Interpret as a cardinal ballot
return BallotLevels(
{c: self.low + my_division((self.high - self.low) * (v - x.scale.low), (x.scale.high - x.scale.low))
for c, v in x.items()},
candidates=x.candidates, scale=self.scale).restrict(candidates=candidates)
except (TypeError, AttributeError):
x_scale = x.scale
if isinstance(x_scale, ScaleFromList):
return BallotLevels(
{c: self.low + my_division(
(self.high - self.low) * x_scale.as_dict[x[c]], (len(x_scale.levels) - 1))
for c, v in x.items()},
candidates=x.candidates, scale=self.scale).restrict(candidates=candidates)
if isinstance(x, BallotOrder):
borda = ScorerBorda(ballot=x, candidates=x.candidates,
unordered_give_points=self.borda_unordered_give_points).scores_
score_max = len(x.candidates) - 1 if self.borda_unordered_give_points else len(x.candidates_in_b) - 1
return BallotLevels(
{c: self.low + my_division((self.high - self.low) * borda[c], score_max) for c in x.candidates_in_b},
candidates=x.candidates, scale=self.scale).restrict(candidates=candidates)
raise NotImplementedError