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copied!<p>Unfortunately, the collections hierarchy got itself into a bit of a mess with <code>-</code> on <code>List</code>. For <code>ArrayBuffer</code> it works just like you might hope:</p> <pre><code>scala> collection.mutable.ArrayBuffer(1,2,3,2,4) - 2 res0: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 3, 2, 4) </code></pre> <p>but, sadly, <code>List</code> ended up with a <code>filterNot</code>-style implementation and thus does the "wrong thing" <em>and</em> throws a deprecation warning at you (sensible enough, since it is actually <code>filterNot</code>ing):</p> <pre><code>scala> List(1,2,3,2,4) - 2 warning: there were deprecation warnings; re-run with -deprecation for details res1: List[Int] = List(1, 3, 4) </code></pre> <p>So arguably the easiest thing to do is convert <code>List</code> into a collection that does this right, and then convert back again:</p> <pre><code>import collection.mutable.ArrayBuffer._ scala> ((ArrayBuffer() ++ List(1,2,3,2,4)) - 2).toList res2: List[Int] = List(1, 3, 2, 4) </code></pre> <p>Alternatively, you could keep the logic of the code you've got but make the style more idiomatic:</p> <pre><code>def removeInt(i: Int, li: List[Int]) = { def removeOne(i: Int, left: List[Int], right: List[Int]): List[Int] = right match { case r :: rest => if (r == i) left.reverse ::: rest else removeOne(i, r :: left, rest) case Nil => left.reverse } removeOne(i, Nil, li) } scala> removeInt(2, List(1,2,3,2,4)) res3: List[Int] = List(1, 3, 2, 4) </code></pre>

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