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

[Paolo Bonzini]

On 12/05/2010 01:14 PM, Dmitry Matveev wrote:
> Hello,
>
> > 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.

Paolo