routing issue

gistfile1.scala

// git clone git@github.com:nafg/reactive.git
// git checkout v0.4.0
// sbt routing/console

import reactive.routing._
implicit object IntArg extends Stringable[Int] { def format = _.toString; def parse = s => util.Try(s.toInt).toOption }
implicit object StringArg extends Stringable[String] { def format = identity; def parse = Option(_) }
val a = arg[Int] >> { i => i.toString }
val b = arg[String] >> { s => s }


(a & b) map identity

/*
error: could not find implicit value for parameter cmr: reactive.routing.CanLiftRouteMapping[reactive.routing.PArg[_ >: String with Int, reactive.routing.PNil]]
*/