Internals
These programs perform character parsing, and tokenizing via the use of a deterministic finite automata (DFA). A DFA is a theoretical machine accepting regular languages. These machines are a subset of the collection of Turing machines. DFAs are equivalent to read only right moving Turing Machines. The syntax is based on the use of Regular expressions. See also nondeterministic finite automaton.
Read more about this topic: Flex Lexical Analyser