Re2c

re2c is a free and open-source software lexer generator for C. Originally written by Peter Bumbulis and described in his paper, it was put in public domain and has been since maintained by volunteers. It is the lexer generator adopted by projects such as PHP, SpamAssassin, ninja build system and others. In combination with Lemon parser generator it is used in BRL-CAD as a platform-agnostic and easily compilable alternative to Flex and Bison. This combination is also used with STEPcode, an implementation of ISO 10303 standard.