Note that the manuals are for different versions of Flex and Bison than
those installed on CLEAR. The differences between versions are minor and
are unlikely to be a major issue in your labs for COMP 506.
Better Error Handling Using Flex and Bison,
Christian Hagen, July 2006. Copyright by IBM Corporation, but
distributed widely through the web.
Nice discussion of how to coordinaate actions between flex scanners
and bison parsers to produce human-friendly error messages.