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).
Intersection. Theorem If L1 and L2 are regular languages, then the new language L = L1 ∩ L2 is regular. Proof By De Morgan's law, L = L1 ∩ L2 = L1 ∪ L2. By the previous two theorems this language is regular.
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.
Regular languages have finite state machines, represent simple patterns, are closed under union, intersection, concatenation, and Kleene star operations.
Closure under Union For any regular languages L and M, then L ∪ M is regular. Proof: Since L and M are regular, they have regular expressions, say: Let L = L(E) and M = L(F). Then L ∪ M = L(E + F) by the definition of the + operator.
Regular languages are closed under complement, union, intersection, concatenation, Kleene star, reversal, homomorphism, and substitution.
Proof: Observe that L \ M = L ∩ M . We already know that regular languages are closed under complement and intersection.
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.
Regular Languages are closed under complementation, i.e., if L is regular then L = Σ∗ \ L is also regular.