Is there way to create tuple from list(without codegeneration)?

Question

Sometimes there are needs to create tuples from small collections(for example scalding framework).

def toTuple(list:List[Any]):scala.Product = ...
         


        

Answer 1

You really don't want your method to return Product since this is uselessly vague. If you want to be able to use the returned object as a tuple, then you'll have to know its arity. So what you can do is have a series of toTupleN methods for different arities. For convenience, you can add these as implicit methods on Seq.

How about this:

class EnrichedWithToTuple[A](elements: Seq[A]) {
  def toTuple2 = elements match { case Seq(a, b) => (a, b) }
  def toTuple3 = elements match { case Seq(a, b, c) => (a, b, c) }
  def toTuple4 = elements match { case Seq(a, b, c, d) => (a, b, c, d) }
  def toTuple5 = elements match { case Seq(a, b, c, d, e) => (a, b, c, d, e) }
}
implicit def enrichWithToTuple[A](elements: Seq[A]) = new EnrichedWithToTuple(elements)

and use it like:

scala> List(1,2,3).toTuple3
res0: (Int, Int, Int) = (1,2,3)