From: stephen.hill@... (Steve Hill)
Date: 2001-07-21T10:07:31+09:00
Subject: [ruby-talk:18220] how does hash locate pairs?

Hi,
in methods such as [], []=, fetch, etc. how does Hash locate a key,
value pair.

For example, in 

h=Hash.new
h[0]="foo"
h[1]="bar"

puts h[0]

how does the Hash object h locate the appropriate pair.

I ask this because I am having problems in getting a hash to work when
the keys are objects that I have created - in this case a Bin_key
object that holds the endpoints of a bin. I've tried defining a == and
a <=> method and I'm not getting anywhere. Here is my bin_key object

(sob story: I'm posting on NT while working on an x-term under exceed
nt and the copy and paste doesn't work, so this is a retype - please
excuse typos!)

class Bin_key
   def initialize(min,max)
      @max=max
      @min=min
   end

   def ==(x)
      x>@min && x<=@max
   end

   def <=>
     if x<@min then return 1
        elsif x>@min && x<=@max then return 0
        return 1
     end
   end
end

now if I define some code to use Bin_key 

h=Hash.new
h[Bin_key.new(1,10)]="Hello World"

h[5]      ->nil!

This is odd since if I write

h.each {|k,v| puts v if k==5}  -> "Hello World"

Can anyone explain what is going on please?

Best regards

Steve