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author | Paul Phillips <paulp@improving.org> | 2012-05-03 17:11:30 -0700 |
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committer | Paul Phillips <paulp@improving.org> | 2012-05-03 17:15:31 -0700 |
commit | 8bc8b83f0bd7daef62b41b4a0c87b4e9b7344284 (patch) | |
tree | 4f445792891bd6945ce8132b97a0231a8cf54392 /test/files/run/reify_lazyevaluation.scala | |
parent | 58f6a1346093db2f407879246884d480ff8d7904 (diff) | |
download | scala-8bc8b83f0bd7daef62b41b4a0c87b4e9b7344284.tar.gz scala-8bc8b83f0bd7daef62b41b4a0c87b4e9b7344284.tar.bz2 scala-8bc8b83f0bd7daef62b41b4a0c87b4e9b7344284.zip |
Moved passing tests from pending to files.
Most are pattern matcher bugs fixed by virtpatmat. A few are reifier,
package object, or miscellaneous. I threw in an original test for
SI-2337, to go with those for SI-1697, SI-3705, SI-4415, and SI-1357,
all of which (in the interests of making sure this basket has all the
eggs) I am closing.
Diffstat (limited to 'test/files/run/reify_lazyevaluation.scala')
-rw-r--r-- | test/files/run/reify_lazyevaluation.scala | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/test/files/run/reify_lazyevaluation.scala b/test/files/run/reify_lazyevaluation.scala new file mode 100644 index 0000000000..1a0c858914 --- /dev/null +++ b/test/files/run/reify_lazyevaluation.scala @@ -0,0 +1,58 @@ +import scala.reflect.mirror._ + +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 +} |