From: Gary Wright <gwtmp01@...>
Date: 2007-03-17T03:28:58+09:00
Subject: Re: Anyone playing with higher order messaging in ruby?


On Mar 16, 2007, at 1:32 PM, Jenda Krynicky wrote:
> it's a shame the builtins do not work like this already. And while  
> it's
> possible to overwrite the "collect", "select" and "reject" in
> Enumerable, to overwrite the "each" you'd (AFAIK) have to touch all  
> the
> individual classes.

Somewhat related....

In Ruby 1.9 iterating methods (I couldn't think of a better term) such
as each, map, and so on return an Enumerator object if a block isn't
provided.  This makes it easier to add the magic dot behavior:

class Enumerable::Enumerator
   def method_missing(*args, &block)
     each { |x| x.send(*args, &block ) }
   end
end

[1,-2,3,-4].map.abs              # [1,2,3,4]
[1,-2,3,-4].map.abs.map.succ     # [2,3,4,5]
%w{mon tue wed}.map.capitalize   # ["Mon", "Tue", "Wed"]`

This works because Enumerable::Enumerator#each returns the original
collection (instead of the iterator) when a block is provided.

[1,2].each.class          # Enumerator
[1,2].each.each.class     # Enumerator
[1,2].each.each {}.class  # Array


Gary Wright