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package strawman.typeclasses
trait SemiGroup[T] {
def append(x: T, y: T): T
}
object SemiGroup {
class Ops {
implicit class InfixAppend[T: SemiGroup](self: T) {
def |+| (other: T): T = implicitly[SemiGroup[T]].append(self, other)
}
}
object ops extends Ops
}
trait Monoid[T] extends SemiGroup[T] {
val id: T
}
object Monoid {
object ops extends SemiGroup.Ops
}
trait Ring[T] extends Monoid[T] {
val zero = id
val one: T
def product(x: T, y: T): T
}
object Ring {
class Ops extends SemiGroup.Ops {
implicit class InfixProduct[T: Ring](self: T) {
def |*| (other: T): T = implicitly[Ring[T]].product(self, other)
}
}
object ops extends Ops
}
object Test {
implicit object StringMonoid extends Monoid[String] {
def append(x: String, y: String): String = x ++ y
val id = ""
}
implicit object IntRing extends Ring[Int] {
def append(x: Int, y: Int) = x + y
val id = 0
val one = 1
def product(x: Int, y: Int) = x * y
}
import Monoid.ops._ // works in dotty, fails in scalac
import Ring.ops._
"abc" |+| "def"
"abc" |+| StringMonoid.id
StringMonoid.id |+| "abc"
1 |+| 2
3 |*| 3
}
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