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add last, sortBy and sorted to NonEmptyList #1578

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merged 4 commits into from
Mar 31, 2017
Merged

add last, sortBy and sorted to NonEmptyList #1578

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22fd6b0
add last, sortBy and sorted to NonEmptyList
julien-truffaut Mar 27, 2017
4709187
update comment for unreachable code and optimise sorted
julien-truffaut Mar 28, 2017
0a35cb2
use pattern match in Nel#last
julien-truffaut Mar 31, 2017
12c95c6
pass Order instance as parameter for sortBy
julien-truffaut Mar 31, 2017
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update comment for unreachable code and optimise sorted
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@julien-truffaut
julien-truffaut committed Mar 30, 2017
commit 4709187f0ab17a60b2b2a35390f2d659dd2304cc
10 changes: 6 additions & 4 deletions core/src/main/scala/cats/data/NonEmptyList.scala
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Expand Up @@ -231,12 +231,11 @@ final case class NonEmptyList[+A](head: A, tail: List[A]) {
* res0: cats.data.NonEmptyList[(Char, Int)] = NonEmptyList((z,1), (a,4), (e,22))
* }}}
*/
def sortBy[B: Order](f: A => B): NonEmptyList[A] = {
def sortBy[B: Order](f: A => B): NonEmptyList[A] =
toList.sortBy(f)(Order[B].toOrdering) match {
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@peterneyens peterneyens Mar 31, 2017 •
edited
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I think we generally use an implicit parameter (instead of a context bound) when we use the type class instance directly?

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let's be consistent

case x :: xs => NonEmptyList(x, xs)
case Nil => sys.error("absurd")
case Nil => sys.error("unreachable: sorting a NonEmptyList cannot produce an empty List")
}
}

/**
* Sorts this `NonEmptyList` according to an `Order`
Expand All @@ -250,7 +249,10 @@ final case class NonEmptyList[+A](head: A, tail: List[A]) {
* }}}
*/
def sorted[AA >: A](implicit AA: Order[AA]): NonEmptyList[AA] =
sortBy(a => a: AA)
toList.sorted(Order[AA].toOrdering) match {
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Should we do AA.toOrdering?

case x :: xs => NonEmptyList(x, xs)
case Nil => sys.error("unreachable: sorting a NonEmptyList cannot produce an empty List")
}

/**
* Groups elements inside of this `NonEmptyList` using a mapping function
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6 changes: 6 additions & 0 deletions tests/src/test/scala/cats/tests/NonEmptyListTests.scala
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Expand Up @@ -244,6 +244,12 @@ class NonEmptyListTests extends CatsSuite {
}
}

test("NonEmptyList#sortBy is consistent with List#sortBy") {
forAll { (nel: NonEmptyList[Int], f: Int => Int) =>
nel.sortBy(f).toList should === (nel.toList.sortBy(f))
}
}


test("NonEmptyList#groupBy is consistent with List#groupBy") {
forAll { (nel: NonEmptyList[Int], f: Int => Int) =>
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