dfa to reg 할때 참고용

 Note: phi is the empty set
        epsilon is the zero length string
        0, 1, a, b, c, are symbols in sigma
        x is a variable or regular expression
        ( ... )( ... ) is concatenation
        ( ... ) + ( ... ) is union
        ( ... )*  is the Kleene Closure = Kleene Star

      (phi)(x) = (x)(phi) = phi

      (epsilon)(x) = (x)(epsilon) = x

      (phi) + (x) = (x) + (phi) = x

      x + x  = x

      (epsilon)* = (epsilon)(epsilon) = epsilon

      (x)* + (epsilon) = (x)* = x*

      (x + epsilon)* = x*

      x* (a+b) + (a+b) = x* (a+b)

      x* y + y = x* y

      (x + epsilon)x* = x* (x + epsilon) = x*

      (x+epsilon)(x+epsilon)* (x+epsilon) = x*

 

(phi)* = epsilon

이게 좀 신기할 따름

 

 

 

 

http://www.csee.umbc.edu/~squire/cs451_l7.html