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BitraverseLaws.scala
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BitraverseLaws.scala
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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.
*/
package cats
package laws
import cats.data.Nested
trait BitraverseLaws[F[_, _]] extends BifoldableLaws[F] with BifunctorLaws[F] {
implicit override def F: Bitraverse[F]
def bitraverseIdentity[A, B](fab: F[A, B]): IsEq[F[A, B]] =
fab <-> F.bitraverse[Id, A, B, A, B](fab)(identity, identity)
def bitraverseCompose[G[_], A, B, C, D, E, H](
fab: F[A, B],
f: A => G[C],
g: B => G[D],
h: C => G[E],
i: D => G[H]
)(implicit G: Applicative[G]): IsEq[G[G[F[E, H]]]] = {
val fg = F.bitraverse(fab)(f, g)
val hi = G.map(fg)(f => F.bitraverse(f)(h, i))
val c =
F.bitraverse[Nested[G, G, *], A, B, E, H](fab)(
a => Nested(G.map(f(a))(h)),
b => Nested(G.map(g(b))(i))
)
hi <-> c.value
}
}
object BitraverseLaws {
def apply[F[_, _]](implicit ev: Bitraverse[F]): BitraverseLaws[F] =
new BitraverseLaws[F] { def F: Bitraverse[F] = ev }
}