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Add Show[List] #601

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Nov 8, 2015
Merged

Add Show[List] #601

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e18d609
Add Show[List]
Nov 6, 2015
0c508f9
Cleanup show implementation for List
Nov 6, 2015
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6 changes: 6 additions & 0 deletions core/src/main/scala/cats/std/list.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ import algebra.std.{ListMonoid, ListOrder}

import cats.data.Streaming
import cats.syntax.order._
import cats.syntax.show._

import scala.annotation.tailrec
import scala.collection.mutable.ListBuffer
Expand Down Expand Up @@ -70,6 +71,11 @@ trait ListInstances extends ListInstances1 {

implicit def listAlgebra[A]: Monoid[List[A]] = new ListMonoid[A]
implicit def listOrder[A: Order]: Order[List[A]] = new ListOrder[A]

implicit def listShow[A:Show]: Show[List[A]] =
new Show[List[A]] {
def show(fa: List[A]): String = s"List(${fa.map(_.show).mkString(", ")})"
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If you're already using mkString: fa.map(_.show).mkString("List(", ", ", ")")

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Oh I forgot you could do that. Thanks will do.

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To save you a comment: I'll do that in the Set PR too :)

}
}

trait ListInstances1 extends ListInstances2 {
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8 changes: 8 additions & 0 deletions tests/src/test/scala/cats/tests/ListTests.scala
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Expand Up @@ -24,4 +24,12 @@ class ListTests extends CatsSuite {
test("toNel on empty list returns None"){
List.empty[Int].toNel should === (None)
}

test("show"){
List(1, 2, 3).show should === ("List(1, 2, 3)")
(Nil: List[Int]).show should === ("List()")
forAll { l: List[String] =>
l.show should === (l.toString)
}
}
}