dfasyn is a tool for building general deterministic finite automata (DFAs) given a description as a non-determinstic finite automaton. In some areas it has more capabilities than lex/flex, e.g. iterated elements can be specified with constraints between them. However, there are several things that have to be done by hand with dfasyn that lex/flex users take for granted.
dfasyn is licensed under the GPL.
Suggestions, bug reports, experiences, praise, complaints etc to the author, please. (Apart from the obvious complaint of "where is the documentation?"!) To obtain my email address, see below (this obfuscation is to thwart spam harvesting).