From: ranx2@... (Ranx)
Date: 2001-07-21T10:07:32+09:00
Subject: [ruby-talk:18221] Re: how does hash locate pairs?

Hi Steve,
You need to have a method (say to_s) in your Class that returns
a string (unique for each min, max pair)

def to_s
    "#{@min}-#{@max}"
end

You could then use
h[Bin_key.new(1,10).to_s]="Hello World"

and later access it as
h["1-10"] (or even h[Bin_key.new(1,10).to_s])

I dont think hash can be indexed by objects. Only by strings.

Ranx






stephen.hill@motorola.com (Steve Hill) wrote in message news:<c230c758.0107190422.77fdf43e@posting.google.com>...
> 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