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eq.scala
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eq.scala
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/*
* Copyright (c) 2015 Miles Sabin
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cats.derived
import cats.Eq
import shapeless._
trait MkEq[T] extends Eq[T]
object MkEq extends MkEqDerivation {
def apply[T](implicit met: MkEq[T]): MkEq[T] = met
}
private[derived] abstract class MkEqDerivation extends MkEq0 {
implicit val mkEqHnil: MkEq[HNil] =
new MkEq[HNil] {
def eqv(a: HNil, b: HNil) = true
}
implicit def mkEqHcons[H, T <: HList](implicit eqH: Eq[H], eqT: MkEq[T]): MkEq[H :: T] =
mkEqHconsBase(eqH, eqT)
implicit val mkEqCnil: MkEq[CNil] =
new MkEq[CNil] {
def eqv(a: CNil, b: CNil) = true
}
implicit def mkEqCcons[L, R <: Coproduct](implicit eqL: Eq[L], eqR: MkEq[R]): MkEq[L :+: R] = mkEqCconsBase(eqL, eqR)
implicit def mkEqGeneric[T, R](implicit gen: Generic.Aux[T, R], eqR: Lazy[MkEq[R]]): MkEq[T] =
new MkEq[T] {
def eqv(a: T, b: T) = eqR.value.eqv(gen.to(a), gen.to(b))
}
}
private[derived] abstract class MkEq0 {
implicit def mkEqHconsFurther[H, T <: HList](implicit eqH: Lazy[MkEq[H]], eqT: MkEq[T]): MkEq[H :: T] = mkEqHconsBase(eqH.value, eqT)
protected def mkEqHconsBase[H, T <: HList](eqH: Eq[H], eqT: MkEq[T]): MkEq[H :: T] =
new MkEq[H :: T] {
def eqv(a: H :: T, b: H :: T) = eqH.eqv(a.head, b.head) && eqT.eqv(a.tail, b.tail)
}
implicit def mkEqCconsFurther[L, R <: Coproduct](implicit eqL: Lazy[MkEq[L]], eqR: MkEq[R]): MkEq[L :+: R] = mkEqCconsBase(eqL.value, eqR)
protected def mkEqCconsBase[L, R <: Coproduct](eqL: Eq[L], eqR: MkEq[R]): MkEq[L :+: R] =
new MkEq[L :+: R] {
def eqv(a: L :+: R, b: L :+: R) = (a, b) match {
case (Inl(l1), Inl(l2)) => eqL.eqv(l1, l2)
case (Inr(r1), Inr(r2)) => eqR.eqv(r1, r2)
case _ => false
}
}
}