regular expression

  REGULAR EXPRESSIONS   Introduction Regular expressions : are text patterns that define the form a text string should have.     Regular expression History Regular expression history goes back to 1943 when neurophysiologist Warren McCulloch and Walter Pitts published logical calculus of the ideas immanent in nervous activity. This paper not only represented the beginning of the regular expression but also proposed the first mathematical model of neural network. The next step in 1956   the mathematician Stephan Kleene wrote   the paper Representation of events in nerve nets and finite automata. where he coined   the term regular sets and regular expressions . In 1968 a legendary pioneer of computer science took Kleen’s work and extending by publishing his studies in the paper regular expression search algorithm . the engineer was Ken Thomson known for the design and his implementation  of Unix , B programming language , U...