From: Robert Feldt <feldt@...>
Date: 2001-10-26T20:16:15+09:00
Subject: [ruby-talk:23424] RCR #50 Simplifying the use of map by adding optional parameter

Hi,

Below is a new RCR. If you feel anything about it please go to

http://www.rubygarden.com/article.php?sid=127

and vote.

Regards,

Robert

RCR #50
-------
Change map to take an optional parameter which is a Symbol which is sent
to each element (as a message). 

Example: 

  [1,2].map(:succ)  #=> [2,3]

I know that you can do it with 

  [1,2].map {|e| e.succ}

but its more than a "shortcut". IMHO its more in line with how map is used
in functional programming languages. 

I'm not sure what should happen if one both gives a parameter and a
block. Either skip the parameter or apply it first? Probably the latter
since you would otherwise not specify the parameter. 

So here's the new semantics I'm asking for (I'm not sure about the extra
args but added them anyway): 

class Array
  def rcr50_map(symbol = nil, *args, &block)
    if symbol.kind_of?(Symbol)
      a = self.map {|e| e.send(symbol, *args)}
    else
      a = self
    end
    a.map(&block)
  end
end

Oh, it should really be Enumerable#map but this is just an example!?