From: Daniel Berger <djberg96@...>
Date: 2006-06-30T20:51:39+09:00
Subject: Re: Symbol#to_proc is just so beautiful

Omer Raviv wrote:
> Berger, Daniel wrote:
>
>   
>> There must be a way to ditch that '&' somehow.  I'd prefer this:
>>
>> [1,2,3].all?(:positive?)
>>     
>
>
> What you are suggesting is basically an expansion of something that was 
> suggested in RCR50 and rejected. 
> (http://www.rcrchive.net/rejected.html#rcr50)
>   
Heh, I'd forgotten it was ever suggested before.
> I like the idea too.  It would be even better if you could also pass 
> parameters along.
>
> Here are a few more examples:
>
> [1,2,3].any?(:>, 4)
>
> [1,2,3].map(:*, 4)   #->  [4,8,12]
>
> people.collect(:name)
>
> people.select(:retired?)
>
> people.sort_by(:age)
>
> favorite_numbers.select(:between?, 100,200)
>
> people.each(:give_compensation, 50)
>
>
> Here's the implementation:
>   

<snip>

Here's my implementation for Array#map.

class Array
   def map(*args)
      array = []
      hash = {}
      current = nil
      args.each{ |arg|
         if arg.is_a?(Symbol)
            hash[arg] = []
            current = arg
         else
            hash[current] << arg
         end
      }

      self.each{ |e|
         hash.each{ |m, params|
            unless params.empty?
               e = e.send(m, *params)
            else
               e = e.send(m)
            end
         }
         yield e if block_given?
         array << e
      }

      array
   end
end

(Logan Capaldo refactored this somewhat)
> Now, I need help. As you may notice - the above only extends Array. If 
> you change "class Array" to "module Enumerable" in the above code, it 
> turns out that Ruby (1.8.4) refuses to let you override methods such as 
> map, while at the same time, "any?" and "all?" work fine. Anyone got a 
> clue as to how I could fix this?
>   
Array#map is overridden in array.c, so modifying it in Enumerable won't 
affect Array.

Regards,

Dan