From: Robert Klemme <bob.news@...>
Date: 2003-10-02T19:05:36+09:00
Subject: Re: Array and hash iteration questions


"Robert Klemme" <bob.news@gmx.net> schrieb im Newsbeitrag
news:blgp2a$bvnb8$1@ID-52924.news.uni-berlin.de...
>
> "Ben Giddings" <bg-rubytalk@infofiend.com> schrieb im Newsbeitrag
> news:3F7B0BAC.7030305@infofiend.com...
> > Robert Klemme wrote:
> > > cases = Hash.new {|h,k| h[k] = [0, 0]}
> >
> > Ah.  I couldn't remember how to use the block form properly.  I'm
> actually
> > going to use:
> >
> > cases = Hash.new {|hash, key| hash[key] = Hash.new(0)}
> >
> > Because it will make some of the later stuff more clear like
> >
> > cases[case]['Number'] += 1
> > cases[case]['Errors'] += 1 if arr[OFFSET] =~ /Error/
>
> No need to use a Hash for this...
>
> Number = 0
> Errors = 1
>
> cases[case][Number] += 1
> cases[case][Errors] += 1 if arr[OFFSET] =~ /Error/
>
> I might be a bit pricky, but storing the array ref saves one hash
lookup.

> It *can* affect performance if you have a large amount of cases...  (see
> below; although the timing is dominated by the iteration here, you can
see
> that the array is faster)

This sentence should really have appeared several lines above: it's the
argument in favour of using arrays instead of hashes for the counters.

Regards

    robert