# !/usr/bin/ruby
#MMM  9/5/2008
# Simulation/Implementation of a DFA in Ruby
# the DFA M=(Q, Sigma, delta, q0, F)
numstates = 4			 # Q = [0, 1, 2, 3]
alphabet = ['a', 'b']		 # Sigma = {a, b}
				 # delta implmented as function  below
q0 = 0				 # Start state is state 0
acceptingState = Array.new(4, 0)
acceptingState[1] = 1		 # F = { 1 }

def delta(state, inputChar)
  case 
  when state == 0 
	case
	when inputChar == 'a' then return 1;
	when inputChar == 'b' then return 3
	end
  when state == 1 
	case
	when inputChar == 'a' then return 2
	when inputChar == 'b' then return 0
	end
  when state == 2 
	case
	when inputChar == 'a' then return 3
	when inputChar == 'b' then return 3
	end
  when state == 3 
	case
	when inputChar == 'a' then return 3
	when inputChar == 'b' then return 3
	end
  else return 999
  end 
end

# Start Simulation
state = 0
print "alphabet = #{alphabet}\n"
print "acceptingState = #{acceptingState}\n"
#
print "Enter the input string: "
line = gets
puts "line=#{line}"
inp = line.chomp.split(//)

# foreach x in inp
inp.each { |x| 
    break x if x =="\n" 
    ###break x if x =='X' 
    nextstate = delta(state, x)
    print "delta(=#{state}, char=#{x}) = #{nextstate}\n"
    state = nextstate
}
if acceptingState[state] == 1 then puts "Accept"
else puts "Reject"
end