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Add scala.runtime.AbstractPartialFunction #5096

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scabug opened this issue Oct 19, 2011 · 2 comments
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Add scala.runtime.AbstractPartialFunction #5096

scabug opened this issue Oct 19, 2011 · 2 comments

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@scabug
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@scabug scabug commented Oct 19, 2011

The attached diff implements a PartialFunction analogue to scala.runtime.AbstractFunctionN. It takes the smallest possible footprint approach to the change, to avoid any possibility of a bare match block being interpreted as a plain Function (rather than properly a PartialFunction).

This trims about 9k of uncompressed class file size from every bare match block used as a PF. It may well speed up the use of PFs, as well, since all the trait stubs are reified in the AbstractPF class and not in every PF.

For scala-library.jar, this reduces total size a very minor amount (60k):

$ ls -l dists/scala-2.10.0.r25850-b20111018225736/lib/scala-library.jar
-rw-r--r-- 1 tvierling tvierling 8697074 2011-10-18 23:13 dists/scala-2.10.0.r25850-b20111018225736/lib/scala-library.jar

$ ls -l build/pack/lib/scala-library.jar
-rw-r--r-- 1 tvierling tvierling 8633048 2011-10-19 15:25 build/pack/lib/scala-library.jar

The gain is much more likely to be noticeable with Lift or other frameworks that work heavily with bare match blocks as PFs. I plan on submitting diffs under separate cover to make explicit use of scala.runtime.AbstractPartialFunction, to trim related cases where code is explicitly inheriting from the PF trait today.

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@scabug scabug commented Oct 19, 2011

Imported From: https://issues.scala-lang.org/browse/SI-5096?orig=1
Reporter: Todd Vierling (tvierling)
Blocks #5097
Attachments:

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@scabug scabug commented Oct 19, 2011

Commit Message Bot (anonymous) said:
(extempore in r25854) AbstractPartialFunction.

Contributed by Todd Vierling with minor mods by extempore. This is an
obvious extension of AbstractFunctionN which I had some issue making
work at the time. Sounds kind of pitiful given that the compiler patch
is about two lines, but let's all agree to believe it was a different
world then.

This example program is impacted as follows:

class A {
  def f: PartialFunction[Any, Int] = { case x: String => 1 }
  def g: PartialFunction[Any, Int] = f orElse { case x: List[_] => 2 }
  def h: PartialFunction[Any, Int] = g orElse { case x: Set[_] => 3 }
}

Before: 34943 bytes of bytecode
After: 4217 bytes of bytecode

A mere 88% reduction in size. "'Tis but a trifle!" Closes #5096, #5097.

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