Playing with generic numbers and collections

gistfile1.scala

  // -----------------------------------------------
  // Generic square method that works with any kind
  // of numerical type
  // -----------------------------------------------
  def square[N](x: N)(implicit n: Numeric[N]) = {
    n.times(x, x)
  }

  square(10d)
  square(BigDecimal(4))
  square(2)

  // -----------------------------------------------
  // apply square on a collection
  // -----------------------------------------------
  def squares[N](x: Iterable[N])(implicit n: Numeric[N]) = x.map(v => n.times(v, v))
  squares(1 :: 2 :: Nil)
  squares(1d :: 2d :: Nil)
  squares(BigDecimal(1) :: BigDecimal(2) :: Nil)

  // -----------------------------------------------
  // Now let's define a generic squares method
  // that can deal with any kind of numerical types and
  // returns exactly the collection type it takes in input
  // -----------------------------------------------
  import scala.collection.generic.CanBuildFrom
  
  def gsquares[N, I[N] <: Iterable[N]](values: I[N])(implicit bf: CanBuildFrom[I[N], N, I[N]], n: Numeric[N]): I[N] = {
    var builder = bf.apply()
    for (value <- values) { builder += n.times(value, value) }
    builder.result
  }
  gsquares(Seq(1,2,3))
  gsquares(List(1,2,3))
  gsquares(Vector(BigDecimal(1),BigDecimal(2),BigDecimal(3)))
  // But it still doesn't work with Arrays
  //gsquares(Array(1,2,3))
  
  // -----------------------------------------------
  // Now the same revisited that works now with
  // any kind of collections and numerical types
  // -----------------------------------------------
  import scala.collection.generic.CanBuildFrom
  
  def asquares[N, C](values: C)
          (implicit c2i: C => Iterable[N], bf: CanBuildFrom[C, N, C],  n: Numeric[N]): C = {
    var builder = bf.apply()
    for (value <- values) { builder += n.times(value, value) }
    builder.result
  }
  
  asquares(Seq(1,2,3))
  asquares(List(1,2,3))
  asquares(Vector(BigDecimal(1),BigDecimal(2),BigDecimal(3)))
  asquares(Array(1,2,3))
  asquares(Set(2,4))