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import java.io.{ ByteArrayOutputStream, PrintStream }
import scala.reflect.runtime.universe._
import scala.reflect.runtime.{universe => ru}
import scala.reflect.runtime.{currentMirror => cm}
import scala.tools.reflect.ToolBox
import scala.reflect.api._
import scala.reflect.api.Trees
import scala.reflect.internal.Types
object Test extends App {
//val output = new ByteArrayOutputStream()
//Console.setOut(new PrintStream(output))
val toolbox = cm.mkToolBox()
val tree = tree_printf(reify("hello %s").tree, reify("world").tree)
val evaluated = toolbox.eval(tree)
//assert(output.toString() == "hello world", output.toString() +" == hello world")
/*
// upd. Oh, good old times, our very-very first experiments with macros :)
macro def printf(format: String, params: Any*) : String = tree_printf(format: Tree, (params: Seq[Tree]): _*)
*/
var i = 0
def gensym(name: String) = { i += 1; TermName(name + i) }
def createTempValDef( value : Tree, tpe : Type ) : (Option[Tree],Tree) = {
val local = gensym("temp")
(
Some(
ValDef(
NoMods
, local
, TypeTree(tpe)
, value
)
)
, Ident(local)
)
}
def tree_printf(format: Tree, params: Tree*) = {
val Literal(Constant(s_format: String)) = format
val paramsStack = scala.collection.mutable.Stack(params: _*)
val parsed = s_format.split("(?<=%[\\w%])|(?=%[\\w%])") map {
case "%d" => createTempValDef( paramsStack.pop, typeOf[Int] )
case "%s" => createTempValDef( paramsStack.pop, typeOf[String] )
case "%%" => {
(None:Option[Tree], Literal(Constant("%")))
}
case part => {
(None:Option[Tree], Literal(Constant(part)))
}
}
val evals = for ((Some(eval), _) <- parsed if eval != None) yield (eval: Tree)
val prints = for ((_, ref) <- parsed) yield
Apply(
Select(
Select(
Ident( TermName("scala") )
, TermName("Predef")
)
, TermName("print")
)
, List(ref)
): Tree
Block((evals ++ prints).toList, Literal(Constant(())))
}
}
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