split6.scala

    case class Symbol() 
    case object Gap extends Symbol 
    case class Nucleotide() extends Symbol
    case object GapN extends Nucleotide 
    case object A extends Nucleotide
    case object G extends Nucleotide
    case object C extends Nucleotide
    case object T extends Nucleotide
    case object AnyGap
    def splitSimplePass6[T >: Symbol](seq: List[T]): List[List[T]] = {
      def isGapType(c : T) = {
        c match {
          case Gap  => true
          case GapN => true
          case _    => false
        }
      }
      val isGap = isGapType(seq(0))
      def isMatch(c : T) = { if (isGap) isGapType(c) else !isGapType(c) }
      val s = seq.takeWhile{ isMatch }
      val tail = seq.takeRight(seq.length - s.length)
      tail match {
        case Nil => s :: Nil
        case _   => s :: splitSimplePass6(tail)
      }
    }