Regular Expressions We use regular expressions to describe tokens of a programming language. A regular expression is built up of simpler regular expressions(using defining rules) Each regular expression denotes a language. A language denoted by a regular expression is called as a regular set. CS308 Compiler Theory 8Regular Expressions • We use regular expressions to describe tokens of a programming language. • A regular expression is built up of simpler regular expressions (using d fi i l ) d efi n ing ru les ) • Each regular expression denotes a language. • A l d t d b l i i ll d A language deno t e d by a regu lar express ion is call e d as a regul t ar se t. CS308 Compiler Theory 8