From: Robert Klemme <shortcutter@...>
Date: 2008-10-01T23:03:31+09:00
Subject: Re: Mode method for Array

2008/10/1 David A. Black <dblack@rubypal.com>:
> Hi --
>
> On Wed, 1 Oct 2008, Robert Klemme wrote:
>
>> 2008/10/1 Erik Veenstra <erikveen@gmail.com>:
>>>
>>> Speed is also the reason for "pre-defining" variables used in
>>> iterations. (6% faster!!)
>>
>> Premature optimization IMHO.
>
> As much as I like inject, I have to say I've always felt that the ones
> that look like this:
>
>  inject({}) {|h,item| do_something; h }
>
> are kind of unidiomatic. Evan Phoenix was saying recently on IRC (I
> hope I'm remembering/quoting correctly) that his rule of thumb was
> that inject was for cases where the accumulator was not the same
> object every time, and that where a single object is having elements
> added to it, an each iteration from the source collection was better.

In that case #map might be more appropriate - at least if the target
collection is an Array.  Btw, did we ever discuss having #map accept a
parameter which defaults to []?  i.e.

module Enumerable
  def map(target = [])
    each {|x| target << yield x}
    target
  end
end

> I tend to agree, though I'm not able to come up with a very technical
> rationale.
>
> What say you, oh inject king?

Um..., I kind of agree about the unidiomaticness. It's ugly.  These
are certainly much nicer

inject(0) {|h,item| item + h }
inject("") {|s,item| s << item }

I have to admit I use it sparingly these days. :-)

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end