From: Keith Fahlgren <keith@...>
Date: 2007-05-26T04:04:08+09:00
Subject: Re: Introducing the "it" keyword

On 5/24/07, Greg Fodor <gfodor@gmail.com> wrote:
> A common pattern seen in a lot of ruby code is:
>
> g(m(x)) if/unless/while/until h(m(x))

Hmm, this really isn't far from the Ruby equivalent of the common
Scheme/Lisp anaphoric-if macro I've always wanted. Here's the On Lisp
snippet about the same:
http://www.bookshelf.jp/texi/onlisp/onlisp_17.html#SEC111 (I picked up
the AIF habbit from a Graham colleague/protoge, so those folks may be
the only ones who use it).


Basically, I just want if to take a block. Here's that expressed as code:

# pretend num_or_nil was very expensive
def num_or_nil
  r = rand(2)
  if r == 1
    1
  else
    nil
  end
end
# => nil
if num_or_nil {|it|
  it + 20
}
# => 21 or nil

HTH,
Keith