From: "Ara.T.Howard" <ahoward@...>
Date: 2003-11-19T04:27:20+09:00
Subject: Re: testing argument type and duck typing, newbie question

On Tue, 18 Nov 2003, Raphael Bauduin wrote:

> I use them as a key to extract an element from a Hash (if arg is a string)
> or from a Array (if arg is an integer).

i do things like this alot too.  in my experience it is easiest to do this
with an object rather than in a procedural way.  i don't know your exact
setup, but it sounds like you are probably tracking things by key and position
so you can maintain an ordered hash (otherwise you'd simply be hashing on int
or string).  why not simply create a class to do the work?  you can put all
the code in one place and even write a unit test for the class.  something
like


  class LookUpTable < Hash
    def ary; @ary ||= []; end
    def [] k; (Numeric === k ? ary : self)[k]; end
    def []= k,v; ary << super; end
  end

  lut = LookUpTable.new
  keys = :a, :b, :c
  keys.each{|k| lut[k] = k.to_s}

  p lut
  lut.size.times{|i| printf "lut[%d] => %s\n", i, lut[i]}

  __END__
  {:b=>"b", :a=>"a", :c=>"c"}
  lut[0] => a
  lut[1] => b
  lut[2] => c



this may not be your exact case but my point is simply this: if you are going
impliment a lookup based on key type, why not build a class that does a lookup
based on key type?  this way the key checking can be done in one place.

it's so easy to crank out classes in ruby that i do it anytime i'm associating
methods with data.

regards.

-a
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