scala-collections

I would like to implement method that takes arbitrary Seq[T] and returns Seq[T] as well. But when String is provided it should also return String . Passing String works due to some implicit conversion from String to WrappedString extends IndexedSeq[Char] , but I get Seq[Char] in return. Is it possible to get String back? val sx: Seq[Int] = firstAndLast(List(1, 2, 3, 4)) val s1: Seq[Char] = firstAndLast("Foo Bar") val s2: String = firstAndLast("Foo Bar") //incompatible types error def firstAndLast[T](seq: Seq[T]) = Seq(seq.head, seq.last) firstAndLast() implementation is irrelevant, it is only

I'm looking at using a DoubleLinkedList . It's remove() method says "Removes the current node from the double linked list." but there are no other references to current in the page. What is the current node, how do I set it, and surely this can't be the only way of removing an item? A DoubleLinkedList is at the same time the list itself and a list node, similar to the :: for a regular List . You can navigate from one cell to the next or to the previous one with next and prev , respectively, and get the value of a cell with elem . scala> val list = collection.mutable.DoubleLinkedList(1,2,3,4,5)

Assume you have a List(1,"1") it is typed List[Any], which is of course correct and expected. Now if I map the list like this scala> List(1, "1") map { | case x: Int => x | case y: String => y.toInt | } the resulting type is List[Int] which is expected as well. My question is if there is an equivalent to map for filter because the following example will result in a List[Any]. Is this possible? I assume this could be solved at compile time and possibly not runtime? scala> List(1, "1") filter { | case x: Int => true | case _ => false | } Daniel C. Sobral Scala 2.9: scala> List(1, "1") collect {

So I've been working with parallel collections in Scala for a graph project I'm working on, I've got the basics of the graph class defined, it is currently using a scala.collection.mutable.HashMap where the key is Int and the value is ListBuffer[Int] (adjacency list). (EDIT: This has since been change to ArrayBuffer[Int] I had done a similar thing a few months ago in C++, with a std::vector<int, std::vector<int> > . What I'm trying to do now is run a metric between all pairs of vertices in the graph, so in C++ I did something like this: // myVec = std::vector<int> of vertices for (std::vector