離散數學(6)

第六章 Languages: Finite State Machines

If ∑ is an alphabet and n ε Z+, we define the powers of ∑ recursively as follows:

1)∑1=∑

2)∑^n+1={xy|x ε ∑, y ε ∑^n} where xy denote the juxtaposition of x and y

For a alphabet ∑ we define ∑0={λ},where λ denotes the empty string—that is, the string consisting of no symbols taken from ∑.

If ∑ is an alphabet

a)∑ +=n=1 to 無限大U∑ n=Un ε z+∑ n

b)∑ *=n=0 to無限大 U∑ n