From: Trans <transfire@...>
Date: 2008-04-04T10:04:18+09:00
Subject: Re: using a range as a key



On Apr 3, 5:30 pm, Alex Wayne <rubyonra...@beautifulpixel.com> wrote:
> Michael Linfield wrote:
> > I'm trying to achieve the effect of having a range of integers as a hash
> > key, possible?
>
> > In effect I've tried:
>
> > range = 12345...12360
>
> > hash = { range => "success!" }
>
> > hash[12349]
>
> > => nil
>
> This won't work.  The range is a specific object, and that whole object
> is the key
> that points to "success!".  SO in order to get success, you would need
> to:
>
>   hash[12345...12360]
>
> Hash won't do this on its own.  Here is one way to go about this:
>
>   class RangedHash
>     def initialize(hash)
>       @ranges = hash
>     end
>
>     def [](key)
>       @ranges.each do |range, value|
>         return value if range.include?(key)
>       end
>       nil
>     end
>   end
>
>   ranges = RangedHash.new(
>     1..10 => 'low',
>     21..30 => 'medium',
>     41..50 => 'high'
>   )
>   ranges[5]  #=> "low"
>   ranges[15] #=> nil
>   ranges[25] #=> "medium"

It's an interesting idea. What is needed is a Hash that can have key
equality redefined. I seem to recall that 1.9 may have something for
this, so as too allow indifferent key access, and it may work here too
(using === instead of ==, or is it eql?) but I haven't explored it
yet.

T.



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> Posted viahttp://www.ruby-forum.com/.