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Date: Tue, 11 Oct 2011 10:44:24 +0200
From: Viktor Hedefalk <hedef...@gmail.com>
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Subject: Re: [Lift] Re: Help understanding RestHelper serve params
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> What Scala magic is it that doesn't require a "," between Nil and 
> JsonGet? I always want to enter it because I'd assume those are 
> separate arguments in some unapply() extractor or other.
>
Actually Peter mentioned that too:

"Great, now this is it! The unapply method takes our mythical Req that 
the handler PartialFunction is referring to and returns an 
Option[(List[String], Req)]. Now, I've never written an unapply method 
that has a Tuple2 in its Option, but apparently if you do then the first 
element can be referenced before the object and the second after."

I looked it up because I had for some reason forgotten about it even 
though I have used the exact same thing with combinator parsers. There 
it's used with a case class ~ for sequential composition which allows 
you to match something like a ~ b ~ c when constructing your AST.

In the lang spec it's described under:

8.1.10 InfixOperationPatterns

http://www.scala-lang.org/sites/default/files/linuxsoft_archives/docu/files/ScalaReference.pdf

It's basically a special case for extractors to allow for infix 
notation. It applies to constructor and extractor patterns. And it's not 
even only for binary patterns, x e (y, z) => e(x, y, z) too. That I 
think would be confusing though� :)

Thanks,
Viktor