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Introduce The Inverse Type #4345
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/* | ||
* Copyright (c) 2015 Typelevel | ||
* | ||
* Permission is hereby granted, free of charge, to any person obtaining a copy of | ||
* this software and associated documentation files (the "Software"), to deal in | ||
* the Software without restriction, including without limitation the rights to | ||
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of | ||
* the Software, and to permit persons to whom the Software is furnished to do so, | ||
* subject to the following conditions: | ||
* | ||
* The above copyright notice and this permission notice shall be included in all | ||
* copies or substantial portions of the Software. | ||
* | ||
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS | ||
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR | ||
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER | ||
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | ||
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | ||
*/ | ||
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package cats | ||
package data | ||
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import cats.kernel.LowerBounded | ||
import cats.kernel.UpperBounded | ||
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object InverseImpl extends InverseInstances with Newtype { | ||
private[data] def unwrap[A](value: Type[A]): A = | ||
value.asInstanceOf[A] | ||
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private[data] def create[A](value: A): Type[A] = | ||
value.asInstanceOf[Type[A]] | ||
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def apply[A](value: A): Inverse[A] = | ||
create(value) | ||
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implicit def catsInverseOps[A](value: Inverse[A]): InverseOps[A] = | ||
new InverseOps[A](value) | ||
} | ||
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sealed class InverseOps[A](val inverse: Inverse[A]) { | ||
def value: A = InverseImpl.unwrap(inverse) | ||
} | ||
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sealed abstract private[data] class InverseInstances extends InverseInstances0 { | ||
implicit def hashAndOrderForInverse[A: Hash: Order]: Hash[Inverse[A]] with Order[Inverse[A]] = | ||
new Hash[Inverse[A]] with Order[Inverse[A]] { | ||
override def hash(x: Inverse[A]): Int = | ||
Hash[A].hash(x.value) | ||
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override def compare(x: Inverse[A], y: Inverse[A]): Int = | ||
Order.reverse[A](Order[A]).compare(x.value, y.value) | ||
} | ||
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implicit def orderingForInverseFromHashAndOrder[A](implicit A: Order[Inverse[A]]): Ordering[Inverse[A]] = | ||
A.toOrdering | ||
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implicit def lowerBoundForInverse[A](implicit | ||
A: UpperBounded[A], | ||
B: PartialOrder[Inverse[A]] | ||
): LowerBounded[Inverse[A]] = | ||
new LowerBounded[Inverse[A]] { | ||
override def partialOrder: PartialOrder[Inverse[A]] = B | ||
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override def minBound: Inverse[A] = | ||
Inverse(A.maxBound) | ||
} | ||
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implicit def upperBoundForInverse[A](implicit | ||
A: LowerBounded[A], | ||
B: PartialOrder[Inverse[A]] | ||
): UpperBounded[Inverse[A]] = | ||
new UpperBounded[Inverse[A]] { | ||
override def partialOrder: PartialOrder[Inverse[A]] = B | ||
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override def maxBound: Inverse[A] = | ||
Inverse(A.minBound) | ||
} | ||
} | ||
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sealed private[data] trait InverseInstances0 extends InverseInstances1 { | ||
implicit def hashAndPartialOrderForInverse[A: Hash: PartialOrder]: Hash[Inverse[A]] with PartialOrder[Inverse[A]] = | ||
new Hash[Inverse[A]] with PartialOrder[Inverse[A]] { | ||
override def hash(x: Inverse[A]): Int = | ||
Hash[A].hash(x.value) | ||
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override def partialCompare(x: Inverse[A], y: Inverse[A]): Double = | ||
PartialOrder.reverse(PartialOrder[A]).partialCompare(x.value, y.value) | ||
} | ||
} | ||
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sealed private[data] trait InverseInstances1 extends InverseInstances2 { | ||
implicit def orderForInverse[A: Order]: Order[Inverse[A]] = | ||
new Order[Inverse[A]] { | ||
override def compare(x: Inverse[A], y: Inverse[A]): Int = | ||
Order.reverse(Order[A]).compare(x.value, y.value) | ||
} | ||
} | ||
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sealed private[data] trait InverseInstances2 extends InverseInstances3 { | ||
implicit def partialOrderForInverse[A: PartialOrder]: PartialOrder[Inverse[A]] = | ||
new PartialOrder[Inverse[A]] { | ||
override def partialCompare(x: Inverse[A], y: Inverse[A]): Double = | ||
PartialOrder.reverse(PartialOrder[A]).partialCompare(x.value, y.value) | ||
} | ||
} | ||
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sealed private[data] trait InverseInstances3 extends InverseInstances4 { | ||
implicit def hashForInverse[A: Hash]: Hash[Inverse[A]] = | ||
new Hash[Inverse[A]] { | ||
override def hash(x: Inverse[A]): Int = | ||
Hash[A].hash(x.value) | ||
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override def eqv(x: Inverse[A], y: Inverse[A]): Boolean = | ||
Hash[A].eqv(x.value, y.value) | ||
} | ||
} | ||
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sealed private[data] trait InverseInstances4 { | ||
implicit def eqForInverse[A: Eq]: Eq[Inverse[A]] = | ||
Eq.by[Inverse[A], A](_.value) | ||
} |
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Looks like
Hash[Inverse[A]].hash <==> Hash[A].hash
so what is the point of having an
Inverse
forHash
then?There was a problem hiding this comment.
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There isn't if you know you're dealing with an
Inverse
. This is provided to solve constraints in a generic context, e.g.def foo[A: Hash]
I want to be able to call that withA
andInverse[A]
for allA
which have aHash
.