From: ara.t.howard@...
Date: 2006-06-02T13:39:00+09:00
Subject: Re: An alternative to the class Foo < Struct.new(vars) idiom and SuperStruct

On Fri, 2 Jun 2006 transfire@gmail.com wrote:

>
> Hal Fulton wrote:
>> That's another example of why I would like a data structure
>> that  1) had a convenient notation for literals and 2) was
>> "like" a Hash, but ordered.
>
> Facet's has Association which gives one something quite like that.
>
>  [ :a >> 1, :b >> 2 ]
>
> Of course it does take over the #>> operator, so it can't be used
> inside any class that defines it. But that's not a big deal. It just
> means you can't _extend_ the following classes with code that uses an
> Association.
>
>  Bignum
>  Fixnum
>  Date
>  IPAddr
>  Process::Status
>
> T.

that just gave me an idea:

     harp:~ > cat a.rb
     require 'arrayfields'
     class Map < Array
       class Pair < Array; end
       def initialize *pairs
         fields = []
         pairs.each{|k, v| self << v and fields << k}
         self.fields = fields
       end
       def self.[](*a, &b) new(*a, &b) end
     end
     class Symbol
       def >(value) Map::Pair[self, value] end
     end
     def Map(*a, &b) Map.new(*a, &b) end
     def map(*a, &b) Map.new(*a, &b) end


     m = map :a > 4, :b > 2
     p m
     p m[:a]
     p m[:b]
     p m.to_hash
     p m.keys


     harp:~ > ruby -r rubygems a.rb
     [4, 2]
     4
     2
     {:b=>2, :a=>4}
     [:a, :b]


what do you think?


-a
-- 
be kind whenever possible... it is always possible.
- h.h. the 14th dali lama