|
The set of all strings over an alphabet ![](eqns/e-2.gif) is denoted by ![](eqns/e-20.gif) . That is,
![](eqns/e-21.gif) The set contains all the strings that can be generated by iteratively concatenating symbols from any number of times.
Example : If = { a, b }, then = { e, a, b, aa, ab, ba, bb, aaa, aab, aba, abb, baa, …}.
Please note that if , then that is . It may look odd that one can proceed from the empty set to a non-empty set by iterated concatenation. But there is a reason for this and we accept this convention. |