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import scala.reflect.runtime.universe._
import scala.tools.reflect.Eval
object Test extends App {
reify {
/* The syntax tree of a toy language */
abstract class Term[T]
/* An integer literal */
case class Lit(x: Int) extends Term[Int]
/* Successor of a number */
case class Succ(t: Term[Int]) extends Term[Int]
/* Is 't' equal to zero? */
case class IsZero(t: Term[Int]) extends Term[Boolean]
/* An 'if' expression. */
case class If[T](c: Term[Boolean],
t1: Term[T],
t2: Term[T]) extends Term[T]
/** A type-safe eval function. The right-hand sides can
* make use of the fact that 'T' is a more precise type,
* constraint by the pattern type.
*/
def eval[T](t: Term[T]): T = t match {
case Lit(n) => n
// the right hand side makes use of the fact
// that T = Int and so it can use '+'
case Succ(u) => eval(u) + 1
case IsZero(u) => eval(u) == 0
case If(c, u1, u2) => eval(if (eval(c)) u1 else u2)
}
println(
eval(If(IsZero(Lit(1)), Lit(41), Succ(Lit(41)))))
}.eval
}
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