Kiama rewrite

gistfile1.scala

scala> import org.kiama.rewriting.Rewriter._
import org.kiama.rewriting.Rewriter._

scala> trait Expr
defined trait Expr

scala> case class Constant(x: Int) extends Expr
defined class Constant

scala> case class Add(e1: Expr, e2: Expr) extends Expr
defined class Add

scala> val e = Add(Constant(1), Constant(2))
e: Add = Add(Constant(1),Constant(2))

scala> val rewritePlus5 = everywheretd (rule { case Constant(x) => Constant(x+5) })
rewritePlus5: org.kiama.rewriting.Rewriter.Strategy = <function1>

scala> rewrite (rewritePlus5) (e)
res0: Add = Add(Constant(6),Constant(7))