Summary

This is a toy model for regular expression.

How it works

These classes construct regular expression using a very simple way.

Formal definition for regular language

• any single letter, empty string $ε$, $∅$ are regular language.
• The kleene Closure of any regular language is regular language.
• The Union of any regular language is regular language.
• The ConCat of any regular language is regular language.

How to implement a finite automata to recognize the regular expression.

Using NFA to simulate the union of the regular language

Using NFA to simulate the concat of the regular language

Using NFA to simulate the kleene closure of the regular language

After the steps above, we just need to implement a bfs to convert the NFA to DFA.