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Expose headOption for Chain #2610

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merged 6 commits into from
Nov 15, 2018
Merged

Expose headOption for Chain #2610

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e92c338
Expose headOption for Chain
ChristopherDavenport Nov 13, 2018
597de6a
Address Whitespace In Line
ChristopherDavenport Nov 14, 2018
f84eb05
Test headOption behavior
ChristopherDavenport Nov 14, 2018
a66a97b
Scalafmt Chain Tests
ChristopherDavenport Nov 14, 2018
0fa5647
Incorporate Better Property Test
ChristopherDavenport Nov 14, 2018
af0a6af
Scalafmt again
ChristopherDavenport Nov 14, 2018
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5 changes: 5 additions & 0 deletions core/src/main/scala/cats/data/Chain.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,11 @@ sealed abstract class Chain[+A] {
result
}

/**
* Returns the head of this Chain if non empty, none otherwise. Amortized O(1).
*/
def headOption: Option[A] = uncons.map(_._1)

/**
* Returns true if there are no elements in this collection.
*/
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6 changes: 6 additions & 0 deletions tests/src/test/scala/cats/tests/ChainSuite.scala
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Expand Up @@ -56,6 +56,12 @@ class ChainSuite extends CatsSuite {
}
}

test("headOption") {
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forAll { (s: Seq[Int]) =>
Chain.fromSeq(s).headOption should ===(s.headOption)
}
}

test("size is consistent with toList.size") {
forAll { (ci: Chain[Int]) =>
ci.size.toInt should ===(ci.toList.size)
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