From: daz <dooby@...10.karoo.co.uk>
Date: 2005-07-13T18:25:51+09:00
Subject: Re: accessing index inside map


Robert Klemme wrote:
> Brian Candler wrote:
>
> > In fact, even
> >
> >   obj.enum(:each_with_index).inject(0) {|sum,(a,i)| sum + a*i}
>
> That reads better IMHO.
>
> > reads better to me, as it's not stressing the creation of an
> > intermediate object. to_foo looks like you are converting obj into
> > something completely different, rather than just adding a temporary
> > wrapper.
>
> Yeah, maybe.  Anyway, this is far better than rename IMHO.
>


[1];  obj.enum(:each_with_index).inject(0) {|sum,(a,i)| sum + a*i}

[2];  i=-1; obj.inject(0) {|sum, a| sum + a*(i+=1)}

Can anyone shade me in on what, if any, advantage [1] has over [2]:
-- in terms of:

 a) Readability
 b) Ease of use and understanding
 c) Performance
 d) Flexibility
 e) Accuracy
 f) Memory usage
 g) Anything else you care to throw in  ;-)

I can tell at a glance that it's going to require more typing
because it contains the string '_with_index' ...

##    keystrokes (including shifts on UK kbd)
#     _with_index  #-> 11/13
#     i=-1; i+=1;  #-> 10/11

But there seem to be so many other overheads in comparison,
that I can't focus on whether or not you're saying something
that I need to get my head around.

TIA,

daz