Regular Expressions
Regular Expressions
If E1 and E2 are regular expressions denoting languages
L(E1) and L(E2), then
- E1 | E2 is a regular expression denoting a language
L(E1) union L(E2).
- E1 E2 is a regular expression denoting a language L(E1)
followed by L(E2).
- E* (E star) is a regular expression denoting L(E star) =
Kleene closure of L(E).
An alphabet symbol,a, is a regular expression.
An empty symbol is also a regular expression.