http://hobbes.nmsu.edu/cgi-bin/h-search?key=bison1875.zip
"Bison is a general-purpose parser generator that converts a grammar description for an LALR context-free grammar into a C program to parse that grammar. Once you are proficient with Bison, you can use it to develop a wide range of language parsers, from those used in simple desk calculators to complex programming languages."
Source: OS2.jp