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Re: [Help-smalltalk] short list of possible smalltalk extensions

From: Paolo Bonzini
Subject: Re: [Help-smalltalk] short list of possible smalltalk extensions
Date: Sun, 05 Dec 2010 13:18:42 +0100
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On 12/05/2010 01:14 PM, Dmitry Matveev wrote:

5.a) Anonymous variables for blocks.

      x select: [ _ even]

As far as I know, the latest VisualWorks support another way to do it:

         x select: #even

I.e. pass a selector symbol, not a block. Just FYI :)

Yes, this is a fairly common extension but it has problems because "#even numArgs" is 0 while "[:a | a even ] numArgs" is one. This is the main reason why GNU Smalltalk does _not_ provide Symbol>>#value (and never will).

However, in my message there's also an alternative way to provide "x select: #even" by tweaking the meaning of #select:'s argument.

BTW, "x select: #even" needs to use reflection so it will always be slower than "x select: [ :a | a even]", especially when using a JIT compiler.


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