ScalaのRegexParsersで書いたパーサのチューニング方法 #2 ref: http://qiita.com/rubyu/items/de843a441859cf81af48

file2.txt

(access count: A,31)
(access count: B,40)

Parser.scala

//適当なCSVパーサの定義
//lazy val field = "[a-z]+".r
lazy val A = field ~ ( rep( "," ~ field ) ).? 
lazy val B = ( rep( field ~ "," ) ).? ~ field

ParserTest.scala

var count = 0
class DebugCharSequence(seq: CharSequence) extends java.lang.CharSequence {
  def charAt(n: Int) = { count += 1; seq.charAt(n) }
  def subSequence(s: Int, e: Int) = new DebugCharSequence(seq.subSequence(s, e))
  def length = seq.length
  override def toString = seq.toString
}
val dseq = new DebugCharSequence("a,b,c")
parser.parse(parser.A, dseq)
println("access count: A", count)
count = 0
parser.parse(parser.B, dseq)
println("access count: B", count)