From: Jamis Buck <jgb3@...>
Date: 2004-10-21T04:12:50+09:00
Subject: Re: each with separator

Charles Mills wrote:
> On Oct 20, 2004, at 11:05 AM, Michael Neumann wrote:
> 
>> Hi,
>>
>> I know we had a similar thread in the past about first/last-element
>> detection.
>>
>> In Smalltalk there's #do:separateBy: which basically works like
>> each+join combined, but in an imperative fashion.
>>
>> Now I tried to implement:
>>
>>   [1,2,3].separate_by { puts "-" }.each {|obj|
>>     puts obj
>>   }
>>
>> desired output:
>>
>>   1
>>   -
>>   2
>>   -
>>   3
>>
> 
> Here is another solution your probably not interested in:
> 
> module Enumerable
>   def separate_by(&block)
>     ary = []
>     each_with_index do |obj, i|
>       ary << block.call if i > 0
>       ary << obj
>     end
>     ary
>   end
> end
> 

Another esoteric solution, which came to me while reading the above 
solution:

   module Enumerable
     def separate_by(&block)
       class << block; def to_s; call; end; end
       inject( [] ) { |a,i| a << block unless a.empty?; a << i }
     end
   end

   puts [ 1, 2, 3 ].separate_by { "-" }

- Jamis

-- 
Jamis Buck
jgb3@email.byu.edu
http://www.jamisbuck.org/jamis