From: Chad Perrin <perrin@...>
Date: 2007-12-14T10:43:17+09:00
Subject: Re: How To Avoid Ugly Declerations

On Thu, Dec 13, 2007 at 05:16:24AM +0900, Michael Boutros wrote:
> Thanks so much for all the replies :) So, what I've gathered is that map 
> basically loops through all the values of an array, does whatever the 
> block says to do, and then places it back into the array. Correct?

If I understand your sentence correctly -- no, that's incorrect.

My understanding is that you expect #map or #collect to do this:

  foo = %w(rgb irs rib)
  foo.map {|f| f.gsub('r', 'e')}
  puts foo
  > egb
  > ies
  > eib

What it actually does is this:

  foo = %w(rgb irs rib)
  bar = foo.map {|f| f.gsub('r', 'e')}
  puts foo
  > rgb
  > irs
  > rib
  puts bar
  > egb
  > ies
  > eib

Thus, the proposed method declaration:

  def some_method(foo)
    foo.map { |f| f.reverse }
  end

. . . would return the reversed list, exactly the same as a version with
an explicit return statement.  It does not alter the provided variable at
all, but instead outputs a brand-new list object.

-- 
CCD CopyWrite Chad Perrin [ http://ccd.apotheon.org ]
They always say that when life gives you lemons you should make lemonade. 
I always wonder -- isn't the lemonade going to suck if life doesn't give
you any sugar?