The Golden Chain εNFA  NFA  DFA  REGEX

Regular Expressions

Computations in a semi-ring Given a weighted graph, find the shortest path connecting any two vertices Given a graph, find its transitive closure Given a finite automaton, find the REGEX describing its language

DFA and REGEX are equivalent!

From DFA ro Regex: Example Will need:

alternative technique: State Elimination

Algebraic laws

Algebraic laws for REGEX

Properties of Regular Languages

The intuition behind the pumping lemma

example

confuting the regularity of a language

The pumping lemma Cannot prove that a language is regular It MIGHT be able to confute that a language is regular It does not state that in any regular language every sufficiently long string z contains a repeated term, i.e., z =xyyw