From: Jim Freeze <jim@...>
Date: 2005-07-06T13:08:53+09:00
Subject: Re: yield does not take a block

* Florian Frank <flori@nixe.ping.de> [2005-06-30 13:31:23 +0900]:

> Adam P. Jenkins wrote:
> 
> >obj.method_that_takes_two_blocks {|a| ... }, {|b| ...}, third_arg
> 
> It is made that way in current Ruby 1.9:
> 
> >> def compose(f, g) { |x| f[g[x]] } end
> => nil
> >> h = compose({ |x| 2 * x }, { |x| x + 1 })
> => #<Proc:0x00540dbc@(irb):8>
> >> h[3]
> => 8

Well, this does not appear to be that new. 1.8.2 does the
same, it just requires the 'lambda' keyword:

  def compose(f, g)
    lambda { |x| f[g[x]] }
  end
  h = compose(lambda { |x| 2 * x }, lambda { |x| x + 1 })
  h[3] #=> 8

However, even with the removal of lambda keyword, I think that
there is a big difference between the 'attached' block and
a block that is just another argument.

  meth( {...}, {...}, ...)

is very different from:

  meth {...} {...} ...

As has been said before, changing to the former, to get
multiple blocks, will change the way ruby is used
and perceived by developers.  And I don't think it 
would be for the better.

-- 
Jim Freeze