From: Robert Dober <robert.dober@...>
Date: 2008-06-12T03:18:53+09:00
Subject: Re: each with else

On Wed, Jun 11, 2008 at 7:19 PM, Martin DeMello <martindemello@gmail.com> wrote:
> On Wed, Jun 11, 2008 at 9:54 AM, Thorsten Müller <thorsten@80beans.com> wrote:
>>
>> hmmmm, maybe the RCR should be even more comprehensive and
>> request for a completely new language construct that would allow
>> to built new core commands, based on multiple blocks.
>> Not only if/then, but case/when also.
>>
>> But that's too much for now, a new each would be enough...
>
> More simply, you can define an Object#if_empty
>
> class Object
>  def if_empty
>    yield if self.empty?
>  end
> end
>
> a.each {|x| do something}.if_empty { do something else }
>
> this relies on the fact that obj#each returns obj.
>
> martin
>
>

Martin I think you did not read my reply reagrding this technique, it
is funny though that you want to define Object#is_empty, I would say
that the Ruby way would be Object#empty?

I gave an implementation for Enumerable#empty? using #last, this was
an error because there is no Enumerable#last, I tested with Range
only.

But the point is that I started to think about "emptiness" as a concept.
The first idea was

class Object
   def empty?; instance_variables.all?{ |ivar| instance_variable_get(
ivar ).nil? } end
end

now one needs to redefine empty? for all classes including Enumerable
of course, because to_a.empty is simply not an option of course. But I
am sure that emptiness might be a concept that could be generalized
from arrays and hashes.

Cheers
Robert


-- 
http://ruby-smalltalk.blogspot.com/

---
As simple as possible, but not simpler.
Albert Einstein