The closure properties of a regular language include union, concatenation, intersection, Kleene, complement , reverse and many more operations.
Regular Languages are closed under intersection, i.e., if L1 and L2 are regular then L1 ∩ L2 is also regular. L1 and L2 are regular • L1 ∪ L2 is regular • Hence, L1 ∩ L2 = L1 ∪ L2 is regular.
A set is closed under an operation if applying that operation to any members of the set always yields a member of the set. For example, the positive integers are closed un- der addition and multiplication, but not divi- sion. Fact. The set of regular languages is closed under each Kleene operation.
What is closure? Recall that a set S is closed under an operation X if the output of X is in S whenever the inputs were in S. So, for example, saying that the regular languages are "closed under union" means that if P and R are regular languages, then so is the union of P and R.
Regular Languages are closed under intersection, i.e., if L1 and L2 are regular then L1 ∩ L2 is also regular. L1 and L2 are regular • L1 ∪ L2 is regular • Hence, L1 ∩ L2 = L1 ∪ L2 is regular.
Regular languages are closed under union, concatenation, star, and complementation.
Regular languages are closed under concatenation - this is demonstrable by having the accepting state(s) of one language with an epsilon transition to the start state of the next language. If we consider the language L = {a^n | n >=0}, this language is regular (it is simply a).
Closure properties on regular languages are defined as certain operations on regular language that are guaranteed to produce regular language. Closure refers to some operation on a language, resulting in a new language that is of the same “type” as originally operated on i.e., regular.
In class, we proved that the set of regular languages is closed under union. The idea behind the proof was that, given two DFAs D1,D2, we could make a new DFA D3 which simultaneously keeps track of which state we're at in each DFA when processing a string.