Regular Expression and its Closure Properties

   Regular Expression and its Closure Properties First of all let's see What is Regular Expression ?                Regular Expression which is also referred as rational expression ,  is a sequence of  characters  that specifies a  search pattern .  A regular expression is an algebraic formula whose value is a pattern consisting of a set of strings, called the language of the expression. or                The language accepted by finite automata can be easily described by simple expressions called Regular Expressions. It is the most effective way to represent any language.        A regular expression can also be described as a sequence of pattern that defines a string.   And these expressions are used to match character combinations in strings.   The languages accepted by finite automata are referred to as Regular languages.  String s...