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#
# Copyright Applied Language Solutions 2012
#
# This file is part of Pypeline.
#
# Pypeline is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Pypeline 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 Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Pypeline. If not, see <http://www.gnu.org/licenses/>.
#
from pypeline.core.arrows.arrow import Arrow, ArrowChoice
from pypeline.core.arrows.kleisli_arrow import KleisliArrow
from pypeline.core.types.either import *
class KleisliArrowChoice(ArrowChoice, KleisliArrow):
def __init__(self, patcher, f):
ArrowChoice.__init__(self)
KleisliArrow.__init__(self, patcher, f)
# left :: a b c -> a (Either b d) (Either c d)
def left(self):
def left_func(either):
if isinstance(either, Left):
return self._func(either.val) >= (lambda a: self._patcher(Left(a)))
elif isinstance(either, Right):
return self._patcher(either)
else:
raise ValueError("Must be of type Either")
return KleisliArrowChoice(self._patcher, left_func)
# right :: a b c -> a (Either d b) (Either d c)
def right(self):
def right_func(either):
if isinstance(either, Right):
return self._func(either.val) >= (lambda a: self._patcher(Right(a)))
elif isinstance(either, Left):
return self._patcher(either)
else:
raise ValueError("Must be of type Either")
return KleisliArrowChoice(self._patcher, right_func)
# (+++) :: a b c -> a b' c' -> a (Either b b') (Either c c')
def __add__(self, other):
if not isinstance(other, KleisliArrowChoice):
raise ValueError("Must be a KleisliArrowChoice")
return self.left() >> other.right()
# (|||) :: a b d -> a c d -> a (Either b c) d
def __or__(self, other):
if not isinstance(other, KleisliArrowChoice):
raise ValueError("Must be a KleisliArrowChoice")
return (self + other) >> KleisliArrow(other._patcher, lambda either: self._patcher(either.val))
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