I haven't run across any rex and racc tutorials online, but there are
is a solid example parser buried inside the rex tarball distribution.
The 'calc3' example consists of two source files:
calc3.rex -> The rex token definitions
calc3.racc -> The racc grammar definitions and executable script
They demonstrate many of the differences in coming from lex and yacc.
If you aren't familiar with the traditionally C-based lex and yacc,
they have been in wide use for a (relatively) long time and are well
documented online. I would suggest starting with their documentation
if you are just getting started with parsers, or even LALR parsers. A
good introduction can be found here:
http://epaperpress.com/lexandyacc/
If you aren't set on using an LALR parser, then the Treetop library is
an interesting alternative. It uses a very different method of
generation, but it's become a popular Ruby tool. It can be found here:
http://treetop.rubyforge.org/
Let us know if this doesn't answer your question. Good luck!
