47 lines
1.8 KiB
Python
47 lines
1.8 KiB
Python
# pyRCV2: Preferential vote counting
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# Copyright © 2020–2021 Lee Yingtong Li (RunasSudo)
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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from pyRCV2.numbers.base import BasePyNum, compatible_types
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from fractions import Fraction
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import math
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class Rational(BasePyNum):
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"""
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Wrapper for Python Fraction (rational arithmetic)
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"""
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_py_class = Fraction # For BasePyNum
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def pp(self, dp):
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"""Overrides BasePyNum.pp"""
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# TODO: Work out if there is a better way of doing this
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return format(float(self.impl), '.{}f'.format(dp))
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def round(self, dps, mode):
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"""Implements BaseNum.round"""
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factor = Fraction(10) ** dps
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if mode == Rational.ROUND_DOWN:
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return Rational._from_impl(math.floor(self.impl * factor) / factor)
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elif mode == Rational.ROUND_HALF_UP: # pragma: no cover
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raise NotImplementedError('ROUND_HALF_UP is not implemented in Python Rational context')
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elif mode == Rational.ROUND_HALF_EVEN:
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return Rational._from_impl(round(self.impl * factor) / factor)
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elif mode == Rational.ROUND_UP:
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return Rational._from_impl(math.ceil(self.impl * factor) / factor)
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else: # pragma: no cover
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raise ValueError('Invalid rounding mode')
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