val evals = ListBuffer[ValDef]()
def precompute(value: Tree, tpe: Type): Ident = {
  val freshName = TermName(c.fresh("eval$"))
  evals += ValDef(Modifiers(), freshName, TypeTree(tpe), value)
  Ident(freshName)
}
val paramsStack = Stack[Tree]((params map (_.tree)): _*)
val refs = s_format.split("(?<=%[\\w%])|(?=%[\\w%])") map {
  case "%d" => precompute(paramsStack.pop, typeOf[Int])
  case "%s" => precompute(paramsStack.pop, typeOf[String])
  case "%%" => Literal(Constant("%"))
  case part => Literal(Constant(part))
}
val stats = evals ++ refs.map(ref => reify(print(c.Expr[Any](ref).splice)).tree)
c.Expr[Unit](Block(stats.toList, Literal(Constant(()))))