compilers@ima.UUCP (01/20/86)
[from allegra!ucbvax!phr (Paul Rubin)] The parsers generated by Bison and Zoo (both written by Bob Corbett and distributed by the Free Software Foundation) are public domain and compatible with YACC parsers (tho they run faster). Bison was written by Bob Corbett as part of his PhD thesis at Berkeley on compiler error recovery. It is a more modern parser generator than Yacc, but used a different input syntax. Stallman got a copy and hacked it up to process Yacc input (along with some extensions), but this was kind of a kludgy job. Then Corbett wrote Zoo (based on Bison), which was intended as a Yacc replacement and may yet replace Yacc on some future BSD tape. However, the GNU C compiler uses Bison's extensions, so until someone hacks them into Zoo (not too difficult from what I've heard.) Bison was on some of the early GNU distribution tapes, but was withdrawn due to bugs. Zoo does not have the bugs (it supports every documented feature of Yacc) but lacks some of Bison's undocumented extensions. They are based on the same code. Some version of Bison and/or Zoo will be GNU's Yacc replacement when GNU is a more complete system.