From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-05-22T08:56:08+09:00
Subject: Re: join not in Enumerable

On Sun, 22 May 2005, Logan Capaldo wrote:

> Just a few minutes ago I was playing with irb as I am wont to do, and
> typed this:
>
> ('a'..'z').join(' ')
>
> Lo and behold it protested at me with a NoMethodError. I said to my
> self, self there is no reason that has to be Array only functionality.
> Why isn't it in Enumerable? So I said:
>
> module Enumerable
>       def join(sep = '')
>            inject do |a, b|
>                     "#{a}#{sep}#{b}"
>            end
>        end
> end
>
> And then I said ('a'..'z').join(' ') and got:
> => "a b c d e f g h i j k l m n o p q r s t u v w x y z"
>
> #inject has to be the most dangerously effective method ever. But I digress:
>
> Why is join, and perhaps even pack in Array and not in Enumerable?

the only reason i can think of is that just because somthing is countable
(Enumerable) doesn't mean each sub-thing is singular.  take a hash for
example.  this is no stubling block (pun intended) for ruby however:

   harp:~ > cat a.rb
   module Enumerable
     def join(sep = '', &b)
       inject(nil){|s,x| "#{ s }#{ s && sep }#{ b ? b[ x ] : x }"}
     end
   end
   class Array; def join(*a, &b); super; end; end

   r = 'a' .. 'z'
   p(r.join(' '))

   h = {:k => :v, :K => :V}
   p(h.join(';'){|kv| kv.join '=>'})

   a = [ [0, 1], [2, 3] ]
   p(a.join(','){|kv| kv.join ':'})


   harp:~ > ruby a.rb
   "a b c d e f g h i j k l m n o p q r s t u v w x y z"
   "k=>v;K=>V"
   "0:1,2:3"

this allows 'nesting' of join calls for arbitrarily deep enumerable structures.

   a3 = [
     [ [:a, :b], [:c, :d] ],
     [ [:e, :f], [:g, :h] ],
   ]

   p( a3.join('___'){|a2| a2.join('__'){|a1| a1.join '_'}} )

   #=> "a_b__c_d___e_f__g_h"

it's a nice idea you have there!

cheers.

-a
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