From: "Brian Schröder" <ruby.brian@...>
Date: 2005-09-10T17:50:09+09:00
Subject: Re: Why? Blocks

On 09/09/05, Joe Van Dyk <joevandyk@gmail.com> wrote:
> On 9/8/05, Jamis Buck <jamis@37signals.com> wrote:
> > On Sep 8, 2005, at 8:49 PM, Julian Leviston wrote:
> >
> > > Why can I not do this:
> > >
> > > c = [1,2,3,4,5,6,6,7,8,10]
> > > b = {|aVal| aVal / 5 == 0}
> > > d = c.select(b)
> > >
> > > I would like to store sections of code so I don't have to repeat
> > > myself...
> >
> > b = Proc.new {|aVal| aVal / 5 == 0}
> > d = c.select(&b)
> 
> What's the significance of '&b' vs 'b'?
> 
> 

There is a similiarity between the star and the ampersand operator. A
star packs and unpacks arrays, while the ampersand packs and unpacks
code. E.g.

$ cat star-ampersand.rb
def another_method(a, b, c)
  yield(:a=>a, :b => b, :c => c)
end

def take_block(*args, &block)
  another_method(*args,  &block)
end

take_block(1,2,3) do | hash | p hash end

$ ruby star-ampersand.rb
{:b=>2, :c=>3, :a=>1}

regards,

Brian


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