FASTA parser in Scala

FASTA.scala

import scala.util.parsing.combinator._

object FASTA {

  case class Entry( description: String, sequence: String )

  def fromFile( fn: String ): List[Entry] = {
    val lines = io.Source.fromFile(fn).getLines.mkString("\n")
    fromString( lines )
  }

  def fromString( input: String ): List[Entry] =
    Parser.parse(input)

  private object Parser extends RegexParsers {

    lazy val header = """>.*""".r ^^ { _.tail.trim }  
    lazy val seqLine = """[^>].*""".r ^^ { _.trim }

    lazy val sequence = rep1( seqLine ) ^^ { _.mkString }

    lazy val entry = header ~ sequence ^^ { 
      case h ~ s => Entry(h,s)
    }

    lazy val entries = rep1( entry )

    def parse( input: String ): List[Entry]  = {
      parseAll( entries, input ) match {
        case Success( es , _ ) => es
        case x: NoSuccess =>  throw new Exception(x.toString)
      }
    }
  }
}

FASTADemo.scala

object FASTADemo extends App {
  
  val fn = args(0)

  val entries = FASTA.fromFile( fn )
  
  for( e <- entries ) {
    println( e.description + " -> " + e.sequence )
  }

}