From: Alex Wayne <rubyonrails@...>
Date: 2008-04-04T06:30:44+09:00
Subject: Re: using a range as a key

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"

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