Subject Build code with lex and yacc
Author marius popa
i think is used for building firebird :)

Build code with lex and yacc, Part 1: Introduction
http://www-106.ibm.com/developerworks/library/l-lexyac.html
Build code with lex and yacc, Part 2: Development and troubleshooting
http://www-106.ibm.com/developerworks/linux/library/l-lexyac2.html