__SymbolTable__ is a handy little Ruby class that was conceived from the union of
[Hash][hash] and [Symbol][symbol]. SymbolTable directly extends Hash, but it stores all keys
internally as symbols. Any key that cannot be converted to a Symbol is not
valid.

While this may seem restrictive, it does have the nice side effect of making
all keys slightly more memorable and usable. For example, values may be set
and retrieved using any key that resolves to the same symbol.

    h = Hash.new
    h[:a] = 1
    h[:a]       # => 1
    h['a']      # => nil
    h.a         # => NoMethodError: undefined method `a' for {}:Hash

    require 'symboltable'

    t = SymbolTable.new
    t[:a] = 1
    t[:a]       # => 1
    t['a']      # => 1
    t.a         # => 1
    t.b = 2     # => 2

Also, because SymbolTable subclasses Hash, you get all the nice methods of Hash
for free.

    t.keys      # => [:a, :b]
    t.values    # => [1, 2]

    t.merge!('c' => 3, :d => 4)
    t.keys      # => [:a, :b, :c, :d]
    t.values    # => [1, 2, 3, 4]

    t.each do |k, v|
      puts "#{k} = #{v}"
    end

You get the idea. This kind of data structure is mainly useful for large
configuration objects and the like, where you want to store a bunch of data and
you don't want to have to remember later how you stored it.

Why?
----

Mainly just for fun, and because I sometimes miss the automatic and ubiquitous
type conversion you get in [PHP][php].

Installation
------------

Using [RubyGems][rg]:

    $ sudo gem install symboltable

From a local copy:

    $ git clone git://github.com/mjijackson/symboltable.git
    $ cd symboltable
    $ rake package && sudo rake install

[hash]: http://ruby-doc.org/core/classes/Hash.html
[symbol]: http://ruby-doc.org/core/classes/Symbol.html
[rg]: http://rubygems.org/
[php]: http://php.net/
