From: "David A. Black" <dblack@...>
Date: 2009-06-24T02:35:37+09:00
Subject: Re: Is it the ruby way to implement #downto

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Hi --

On Wed, 24 Jun 2009, Skye Shaw!@#$ wrote:

> On Jun 23, 8:36�am, Li Chen <chen_...@yahoo.com> wrote:
>> Hi all,
>>
>> I wonder if the following code is the ruby way to implement
>> Integer#downto.
>> #######################
>> class Integer
>> � def my_downto(final=2)
>> � � for i in (final..self).to_a.reverse
>> � � � yield i
>> � � � end
>> � �end
>> �end
>>
>> �10.my_downto(-1) do |i| puts i end
>
> Well, I'd hope that creating 3 unnecessary objects wouldn't be deemed
> the Ruby way :^)
> Most code I've seen would use each() instead of for i in (). Each is
> faster anyways.
>
> Why not use the bastardized C way:
>
> class Integer
> � def my_downto(final=2)
>     i = self
>     while i >= final
>      yield i
>      i-=1
>     end
>   end
> end
>
> I don't believe the Ruby community has shunned the idea of writing C
> in ruby have they?

I think most of us shun doing the heavy lifting when Ruby can do it
for us :-) There's nothing C-specific about using an explicit loop
variable, but it's pretty uncommon in Ruby code, except when doing
exercises like implementing each without recourse to each and things
like that.

I'd be tempted to do something like:

   def my_downto(n)
     (self-n+1).times {|x| yield self-x }
     self
   end

I don't know how it performs compared to the others.


David

-- 
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