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Fix bug with Streaming#thunk. #683

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Nov 20, 2015
Merged

Fix bug with Streaming#thunk. #683

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0278d90
Fix bug with Streaming#thunk.
non Nov 19, 2015
60f0686
Add test case to prove this is fixed.
non Nov 19, 2015
e22c15d
Fix documentation for .thunk.
non Nov 19, 2015
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6 changes: 3 additions & 3 deletions core/src/main/scala/cats/data/Streaming.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -808,11 +808,11 @@ object Streaming extends StreamingInstances {
* Continually return the result of a thunk.
*
* This method only differs from `continually` in that the thunk may
* not be pure. The stream is memoized to ensure that repeated
* traversals produce the same results.
* not be pure. Thus, repeated traversals may produce different
* results.
*/
def thunk[A](f: () => A): Streaming[A] =
knot(s => Cons(f(), s), memo = true)
knot(s => Cons(f(), s), memo = false)

/**
* Produce an infinite stream of values given an initial value and a
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10 changes: 10 additions & 0 deletions tests/src/test/scala/cats/tests/StreamingTests.scala
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Expand Up @@ -157,6 +157,16 @@ class AdHocStreamingTests extends CatsSuite {
}
}

test("thunk is evaluated for each item") {
// don't want the stream to be too big
implicit val arbInt = Arbitrary(Gen.choose(-10, 20))
forAll { (start: Int, end: Int) =>
var i = start - 1
val stream = Streaming.thunk{ () => i += 1; i}.takeWhile(_ <= end)
stream.toList should === ((start to end).toList)
}
}

test("interval") {
// we don't want this test to take a really long time
implicit val arbInt: Arbitrary[Int] = Arbitrary(Gen.choose(-10, 20))
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