= characterizable

"Cognitive mechanisms, on this view, take mathematically characterizable inputs to deliver mathematically characterizable outputs, and qua computational devices, that is all."

http://tinyurl.com/28tcrw2

== What is a BetterHash?

It just brings some Ruby 1.9 behavior to Ruby 1.8 hashes... (from http://webonrails.com/2009/02/06/ruby-191-hash)

    RUBY_VERSION => 1.8.6
    >> hash = {:a=> 1, :b=>2, :c=>3, :d=>4}
    => {:b=>2, :c=>3, :d=>4, :a=>1}
    >> hash.select{|k,v| k == :c }
    => [[:c, 3]]

    RUBY_VERSION => 1.9.1
    >> hash = {:a=> 1, :b=>2, :c=>3, :d=>4}
    => {:a=>1, :b=>2, :c=>3, :d=>4}
    >> hash.select{|k,v| k == :c }
    => {:c=>3}

I hope these two tests show the value of BetterHash in the context of this gem...

    should "not be annoying to work with characteristics on a particular instance" do
      a = SimpleAutomobile.new
      a.make = 'Nissan'
      assert_same_contents [:make], a.characteristics.effective.keys
      assert_same_contents [:make], a.characteristics.effective.select { true }.keys
    end

    should "not be annoying to work with characteristics hashes on a class level"
      assert_same_contents [:make, :model, :variant], SimpleAutomobile.characteristics.keys
      assert_same_contents [:make, :model, :variant], SimpleAutomobile.characteristics.select { true }.keys
    end

If you didn't have BetterHash, you wouldn't be able to call <tt>#keys</tt> because in Ruby 1.8 <tt>Hash#select</tt> (and <tt>#reject</tt>) gives you back an Array.

== What is a Snapshot?

It's a hash of the characteristics at a particular time...

    should "keep snapshots separately" do
      my_car = Automobile.new
      my_car.make = 'Ford'
      my_car.model_year = 1999
      snapshot = my_car.characteristics
      assert_same_contents [:make, :model_year], snapshot.effective.keys
      my_car.make = nil
      assert_same_contents [], my_car.characteristics.effective.keys           # up to date!
      assert_same_contents [:make, :model_year], snapshot.effective.keys       # frozen in time!
    end

There are two important points here:

* If you call <tt>my_car.characteristics</tt>, you will always get the most recent snapshot
* If you save the output to a variable like <tt>snapshot</tt>, that snapshot won't change

== Note on Patches/Pull Requests
 
* Fork the project.
* Make your feature addition or bug fix.
* Add tests for it. This is important so I don't break it in a
  future version unintentionally.
* Commit, do not mess with rakefile, version, or history.
  (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
* Send me a pull request. Bonus points for topic branches.

== Copyright

Copyright (c) 2010 Seamus Abshere. See LICENSE for details.