Advanced Lesson 1
Regular Expressions
Chapter 1: Regular expressions?
Regular?
You might be wondering about the term ‘regular’. Here is a brief history lesson in case you are interested!
The term was coined by Mathematician Stephen Cole Kleene in a 1951 paper. Here, he tried to define a formal language for what he called “regular events”, in the context of artificial neurons (you know, the one in Neural Networks).
Regular languages is the most restrictive class of formal grammars in the Chomsky hierarchy. The Chomsky hierarchy ranks different formal languages by their expressiveness, with “recursively enumerable” languages representing all formal languages that can be computed by a computer. There is a whole field called Theory of Computation dedicated to this topic, if you are interested. It is in fact one of my personal favourite Theoretical Computer Science topics!
