From: Carlos <angus@...>
Date: 2001-11-22T22:01:29+09:00
Subject: [ruby-talk:26133] Re: Community spike: Fast-state-machines/goto challenge

> What's your best ideas for how to implement this? Start brainstorming; 
> when/if we get a fairly complete list I'll benchmark the ideas and come 
> back with the figures. Or you can write code yourself. This can be fun!

Here is a simple straightforward approach, from a person who doesn't have
any expertise in the subject. You can use it to test how much faster the
others are ;).

Btw, your test program failed with my rubyunit 0.4.6. I had to change
initialize to

def initialize (a,b)
	super(a,b)
	[etc...]
end

Here's my class:

class StateMachine
	def initialize (start_state, definition)
		# flatten definition
		@states=[]
		definition.each do |d|
			id_state = d[0]
			state_def = {}
			d[1] && d[1].each do |token,next_state|
				if Array===token
					token.each do |t|
						state_def[t]=next_state
					end
				else
					state_def[token]=next_state
				end
			end
			@states << [id_state, state_def]
		end
		# convert id_states into references
		@states.each do |st|
			st[1].each_key do |k|
				st[1][k] = get_state(st[1][k])
			end
		end
		@state=get_state(start_state)
	end
	
	def get_state (id_state)
		@states.detect { |st| st[0] == id_state }
	end
	private :get_state
	
	def states
		@states.collect { |st| st[0] }
	end
	
	def state
		@state[0]
	end
	
	def run (program)
		program.each do |token|
			@state=@state[1][token]
		end
	end
end