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davidandrzej/seq-union.scala

Created December 9, 2012 18:25
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Scala Seq.union behavior - come on!
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seq-union.scala
scala> val x = Seq(1,2)
x: Seq[Int] = List(1, 2)
scala> val y = Seq(2,3)
y: Seq[Int] = List(2, 3)
scala> x.union(y)
res0: Seq[Int] = List(1, 2, 2, 3)
@rcoh
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rcoh commented Jul 30, 2015

the confusing bit is that the method is called union? And it doesn't remove duplicates? It seems pretty reasonable otherwise?

@hardproblems
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is it because Seq is not Set? In any case it is indeed unexpected.

@davidandrzej
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Yeah IMO union is pretty suggestive naming for this method which would lead me to believe it had Set.union semantics. The Scala collection docs finesse this by saying Seq.union is multiset-union, but I guess it would surprise me especially if IntelliJ autocomplete helped me call union on a datatype which I didn't explicitly realize to be Seq...

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