From: MenTaLguY <mental@...>
Date: 2008-02-21T08:12:48+09:00
Subject: Re: IP Address to Decimal - inject sucks

On Thu, 21 Feb 2008 07:10:25 +0900, Ryan Davis <ryand-ruby@zenspider.com> wrote:
> On Feb 20, 2008, at 11:50 , Alex Shulgin wrote:
>> Everybody replied already, still I think left-shift deserves
>> mentioning:
>>
>> "127.0.0.1".split('.').inject(0) { |s,x| (s << 8) + x.to_i }
>> => 2130706433
> 
> It does, and it is the only inject form I consider valid. However,
> converting it to map leads to a 20-25% reduction in time.

Since we aren't using map's result, why not each?

 # of iterations = 1000000
                             user     system      total        real
 null_time               0.218000   0.000000   0.218000 (  0.219000)
 split/each/<<+         24.516000   0.140000  24.656000 ( 24.703000)
 split/map/<<+          26.109000   0.172000  26.281000 ( 26.281000)
 split/inject/<<+       30.797000   0.172000  30.969000 ( 31.000000)

Being an FP nut used to using folds, I'm always a little annoyed that
inject fares so poorly in these things; mainly we're just lacking a
C implementation of Array#inject.

-mental