Flex and Bison are unix utilities that can help you to write very fast parsers for arbitrary file formats. If your synaptic package manager currently does not include these packages, you can install Flex and Bison through a simple terminal command.
This method is specific to Ubuntu 10.4 but should also work for later versions.
Installation of Flex and Bison in Ubuntu
Open a terminal by pressing [CTRL] + [ALT] + T. Then, type one of the the following commands.