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author | Jason Zaugg <jzaugg@gmail.com> | 2012-09-29 18:15:15 +0200 |
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committer | Jason Zaugg <jzaugg@gmail.com> | 2012-11-04 21:21:51 +0100 |
commit | bc3dda2b0222d3b7cf3db491728b98f9b6110856 (patch) | |
tree | d71d81b7c443e75e12da82e9d6e8c53c84d31f1d /test | |
parent | 2c6777fd53b93b95a261aadc87a5cbc03c14d503 (diff) | |
download | scala-bc3dda2b0222d3b7cf3db491728b98f9b6110856.tar.gz scala-bc3dda2b0222d3b7cf3db491728b98f9b6110856.tar.bz2 scala-bc3dda2b0222d3b7cf3db491728b98f9b6110856.zip |
SI-6448 Collecting the spoils of PartialFun#runWith
Avoids calling both `isDefinedAt` and `apply`. This pathological
case that would benefit the most looks like:
xs collect {
case x if {expensive(); true} => x
}
The typical change looks like:
- for (x <- this) if (pf.isDefinedAt(x)) b += pf(x)
+ foreach(pf.runWith(b += _))
Incorporates feedback provided by Pavel Pavlov:
https://github.com/retronym/scala/commit/ef5430
A few more opportunities for optimization are noted in the
`Pending` section of the enclosed test. `Iterator.collect`
would be nice, but a solution eludes me.
Calling the guard less frequently does change the behaviour
of these functions in an obervable way, but not contravene
the documented semantics. That said, there is an alternative
opinion on the comment of the ticket:
https://issues.scala-lang.org/browse/SI-6448
Diffstat (limited to 'test')
-rw-r--r-- | test/files/run/t6448.check | 32 | ||||
-rw-r--r-- | test/files/run/t6448.scala | 61 |
2 files changed, 93 insertions, 0 deletions
diff --git a/test/files/run/t6448.check b/test/files/run/t6448.check new file mode 100644 index 0000000000..9401568319 --- /dev/null +++ b/test/files/run/t6448.check @@ -0,0 +1,32 @@ + +=List.collect= +f(1) +f(2) +List(1) + +=List.collectFirst= +f(1) +Some(1) + +=Option.collect= +f(1) +Some(1) + +=Option.collect= +f(2) +None + +=Stream.collect= +f(1) +f(2) +List(1) + +=Stream.collectFirst= +f(1) +Some(1) + +=ParVector.collect= +(ParVector(1),2) + +=ParArray.collect= +(ParArray(1),2) diff --git a/test/files/run/t6448.scala b/test/files/run/t6448.scala new file mode 100644 index 0000000000..4d1528e500 --- /dev/null +++ b/test/files/run/t6448.scala @@ -0,0 +1,61 @@ +// Tests to show that various `collect` functions avoid calling +// both `PartialFunction#isDefinedAt` and `PartialFunction#apply`. +// +object Test { + def f(i: Int) = { println("f(" + i + ")"); true } + class Counter { + var count = 0 + def apply(i: Int) = synchronized {count += 1; true} + } + + def testing(label: String)(body: => Any) { + println(s"\n=$label=") + println(body) + } + + def main(args: Array[String]) { + testing("List.collect")(List(1, 2) collect { case x if f(x) && x < 2 => x}) + testing("List.collectFirst")(List(1, 2) collectFirst { case x if f(x) && x < 2 => x}) + testing("Option.collect")(Some(1) collect { case x if f(x) && x < 2 => x}) + testing("Option.collect")(Some(2) collect { case x if f(x) && x < 2 => x}) + testing("Stream.collect")((Stream(1, 2).collect { case x if f(x) && x < 2 => x}).toList) + testing("Stream.collectFirst")(Stream.continually(1) collectFirst { case x if f(x) && x < 2 => x}) + + import collection.parallel.ParIterable + import collection.parallel.immutable.ParVector + import collection.parallel.mutable.ParArray + testing("ParVector.collect") { + val counter = new Counter() + (ParVector(1, 2) collect { case x if counter(x) && x < 2 => x}, counter.synchronized(counter.count)) + } + + testing("ParArray.collect") { + val counter = new Counter() + (ParArray(1, 2) collect { case x if counter(x) && x < 2 => x}, counter.synchronized(counter.count)) + } + + object PendingTests { + testing("Iterator.collect")((Iterator(1, 2) collect { case x if f(x) && x < 2 => x}).toList) + + testing("List.view.collect")((List(1, 2).view collect { case x if f(x) && x < 2 => x}).force) + + // This would do the trick in Future.collect, but I haven't added this yet as there is a tradeoff + // with extra allocations to consider. + // + // pf.lift(v) match { + // case Some(x) => p success x + // case None => fail(v) + // } + testing("Future.collect") { + import concurrent.ExecutionContext.Implicits.global + import concurrent.Await + import concurrent.duration.Duration + val result = concurrent.future(1) collect { case x if f(x) => x} + Await.result(result, Duration.Inf) + } + + // TODO Future.{onSuccess, onFailure, recoverWith, andThen} + } + + } +} |