Scala cannot map list of doubles

Question

I have a case class with a property location, which is a tuple2 instance containing doubles.

I first convert it to a list using the following:

testPlace.location.productIterator.toList

This produces a two element list,

List(78.0342, -139.2234)

Running a simple map across this list seems to fail, raising the following compilation error:

loc.map((x:Double) => x + 10.0)

 type mismatch;
   found   : Double => Double
   required: Any => ?
          loc.map( (x:Double) => x + 10.0 )

Can someone explain the rationale behind this and what is wrong with my syntax? What is that required type signature trying to tell me?

Answer 1

Product2.productIterator returns Iterator[Any], so the actual type of your list is List[Any]. This is why your map function is expecting a Any => ?.

http://www.scala-lang.org/api/current/index.html#scala.Product2

Answer 2

Use pattern matching (case)

loc map {case (x:Double) => x + 10.0}