From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-10-12T14:01:03+09:00
Subject: Re: small array/hash question

On Wed, 12 Oct 2005, Kev Jackson wrote:

> I got the output I wanted with this
>
> work_types = Hash.new
> if work_types.has_key?(nsc_id) then
>   work_types[nsc_id]= work_types[nsc_id].include?(work_type) ? 
> work_types[nsc_id] : work_types[nsc_id] << work_type
> else
>   work_types[nsc_id]= [work_type]
> end
>
> So the problem is solved, but I wonder if there's a more elegant way of
> doing it (especially the check to see if the value is already in the array).
> My first assumption was that assignment to a Hash took a block (hence the
> pseudo code), I was actually a little suprised that it didn't ;)

this is one easy way

   work_types = Hash::new{|h,k| h[k] = []}

   work_types[ nsc_id ].push( work_type ).uniq!


but does a bit of extra work.  another way would be to use set

   require 'set'

   work_types = Hash::new{|h,k| h[k] = Set::new}

   work_types[ nsc_id ] << work_type

but you must understand set and it's notion of equality.  plus you lose data
order but, since you are ignoring dups, i guess this isn't important.

or perhaps you can model your data with a nested hash?

   work_types = Hash::new{|h,k| h[k] = {}}

   work_types[ nsc_id ][ work_type ] = true

and then use

   values = work_types[ nsc_id ].keys

or just make your own apprach more compact

   work_types = Hash::new

   work_types[ nsc_id ] = [ work_types[ nsc_id ], work_type ].compact.uniq

you have options - and there is always sqlite if you start to feel like you
are rolling query logic on top of this data structure ;-)

regards.

-a
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