From: dblack@...
Date: 2007-01-12T23:22:22+09:00
Subject: Re: RCR Opinion Poll

Hi --

On Fri, 12 Jan 2007, Alexandru E. Ungur wrote:

>>>> sender: "Robert Dober" date: "Fri, Jan 12, 2007 at 06:56:08PM +0900" <<<EOQ
>> [..]
>>
>> The following is a very common pattern.
>>
>>    an_enum.map{ |ele| ele.a_method }
>>
>> I believe that it is sufficiently common to be generalized.
>>
>> There are two idioms I would like to see
>>
>>   an_enum.apply_to_all :a_method
>
> Ok, I'm still a newbie, but why not extend map instead of introducing a
> new method? As in:
>
>    %w[apples oranges kiwi].map :capitalize  # => ["Apples", "Oranges", "Kiwi"]
>
> Still feels like the good old "map" and acts like it...

I know it's sometimes hard to dig up the old RCRs (this one goes back
two incarnations) but that was rejected; see
http://oldrcrs.rubypal.com/rejected.html#rcr50.

The discussion for that RCR included:

   * the suggestion of map(&:meth)
   * using "apply" instead of "map" as the name
   * rejection by Matz :-)

The reason for rejection was: "It's too functional so that I'm afraid
it would not work well with OO nature of Ruby. Maybe it's matter of
notation."

Ruby 1.9 has the map(&:meth) notation.  I'm not its biggest fan
(mostly on aesthetic/visual grounds), but it has the advantage of
being more generalized.  & invokes to_proc on its operand; and to_proc
for symbols is defined as:

   lambda {|e| e.send(self) }

There's a lot you have to "just know" to grasp what map(&:meth) is
doing, but basically it does this same thing of distributing a
symbolically-identified method across an enumerable.


David

-- 
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A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
    (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
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A. Ruby Power and Light, LLC (http://www.rubypal.com)