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April 11, 2017 15:38
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Implicit isomorphisms with ScalaZ
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import scalaz.Isomorphism.<=> | |
/** Our example Isomorphism */ | |
trait StringIntIso { | |
implicit object StringIntIso extends (String <=> Int) { | |
override val to: (String) => Int = _.toInt | |
override val from: (Int) => String = _.toString | |
} | |
} | |
/** This will not behave as expected */ | |
trait ImplicitIsomorphismsFail { | |
implicit def impliedTo[A, B](a: A)(implicit iso: A <=> B): B = iso.to(a) | |
implicit def impliedFrom[A, B](b: B)(implicit iso: A <=> B): A = iso.from(b) | |
} | |
trait ImplicitIsomorphismsSuccess { | |
/** We only need one direction due to [[scalaz.Isomorphism.isoCommutative]] */ | |
implicit def impliedIso[A, B](a: A)(implicit iso: A <=> B): B = iso.to(a) | |
} | |
object Foo extends ImplicitIsomorphismsFail with StringIntIso { | |
// Do not compile | |
// val x: StringValue = "asdf" | |
// val y: String = x | |
} | |
object Bar extends ImplicitIsomorphismsSuccess with StringIntIso { | |
val x: Int = "asdf" | |
val y: String = x | |
} | |
object BarDesugar extends ImplicitIsomorphismsSuccess with StringIntIso { | |
val x: Int = BarDesugar.impliedIso("asdf")(BarDesugar.StringIntIso) | |
val y: String = BarDesugar.impliedIso(BarDesugar.x)(scalaz.Isomorphism.isoCommutative) | |
} |
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