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author | Dmitry Petrashko <dmitry.petrashko@gmail.com> | 2015-05-12 18:30:53 +0200 |
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committer | Dmitry Petrashko <dmitry.petrashko@gmail.com> | 2015-05-12 18:30:53 +0200 |
commit | 89bacb9c25a58454ff1878e67f7ea07ffc8c269f (patch) | |
tree | 51f1ff6c66aebe1b6109b1cffcc2bb8e4cf760a3 /tests/pending/run/reify_lazyevaluation.scala | |
parent | a0fa33deafbea1bf53edc068c5ed9db5592822f9 (diff) | |
download | dotty-89bacb9c25a58454ff1878e67f7ea07ffc8c269f.tar.gz dotty-89bacb9c25a58454ff1878e67f7ea07ffc8c269f.tar.bz2 dotty-89bacb9c25a58454ff1878e67f7ea07ffc8c269f.zip |
Run tests as they were in scala.
Diffstat (limited to 'tests/pending/run/reify_lazyevaluation.scala')
-rw-r--r-- | tests/pending/run/reify_lazyevaluation.scala | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/tests/pending/run/reify_lazyevaluation.scala b/tests/pending/run/reify_lazyevaluation.scala new file mode 100644 index 000000000..3f2530dde --- /dev/null +++ b/tests/pending/run/reify_lazyevaluation.scala @@ -0,0 +1,61 @@ + +import scala.language.{ implicitConversions } +import scala.reflect.runtime.universe._ +import scala.tools.reflect.Eval + +object Test extends App { + reify { + object lazyLib { + + /** Delay the evaluation of an expression until it is needed. */ + def delay[A](value: => A): Susp[A] = new SuspImpl[A](value) + + /** Get the value of a delayed expression. */ + implicit def force[A](s: Susp[A]): A = s() + + /** + * Data type of suspended computations. (The name froms from ML.) + */ + abstract class Susp[+A] extends Function0[A] + + /** + * Implementation of suspended computations, separated from the + * abstract class so that the type parameter can be invariant. + */ + class SuspImpl[A](lazyValue: => A) extends Susp[A] { + private var maybeValue: Option[A] = None + + override def apply() = maybeValue match { + case None => + val value = lazyValue + maybeValue = Some(value) + value + case Some(value) => + value + } + + override def toString() = maybeValue match { + case None => "Susp(?)" + case Some(value) => "Susp(" + value + ")" + } + } + } + + import lazyLib._ + + val s: Susp[Int] = delay { println("evaluating..."); 3 } + + println("s = " + s) // show that s is unevaluated + println("s() = " + s()) // evaluate s + println("s = " + s) // show that the value is saved + println("2 + s = " + (2 + s)) // implicit call to force() + + val sl = delay { Some(3) } + val sl1: Susp[Some[Int]] = sl + val sl2: Susp[Option[Int]] = sl1 // the type is covariant + + println("sl2 = " + sl2) + println("sl2() = " + sl2()) + println("sl2 = " + sl2) + }.eval +} |