From: Brian Mitchell <binary42@...>
Date: 2005-12-13T08:53:19+09:00
Subject: Re: Idiom wanted: do-while

On 12/12/05, ara.t.howard@noaa.gov <ara.t.howard@noaa.gov> wrote:
>    harp:~ > cat a.rb
>    i = 0
>
>    (
>      p i
>      i += 1
>    ) while i < 3
>
>
>    harp:~ > ruby a.rb
>    0
>    1
>    2

Not quite. That is just a while loop:

( puts "foo" ) while nil
.. nil

which is as always, equivalent to:

while nil
  puts "foo"
end


If you really need a do while loop it is not hard to use loop to
accomplish what you need. If you want something more complex you could
easily get this to work:

lambda do
 ...
end.while { ... }

All you would need is something like this:

class Proc
  def while
    loop do
      result = call
      return result unless yield
    end
  end
end

I am sure there is plenty of room for improving this example too.

Brian.