[5][6] In 1985, Robert Corbett developed an original LALR parser generator based on a 1982 paper by DeRemer and Pennello.

[7] Corbett wrote it as part of his research towards the Ph.D. he received from University of California, Berkeley in June 1985.

Later in 1985, Corbett developed his LALR parser generator, making it Yacc-compatible and naming it Zeus but subsequently renaming it Zoo.

[16][17] However, it has also been criticized for needing side-effect free trial actions and its inflexible handling of shift-reduce conflicts.

[18] In 1997, Vadim Maslov took over maintenance of BtYacc to support a COBOL parser developed by his company.

[28] In 2003, Dave Bodenstab merged tyacc and p5yacc to develop a PERL-TCL-YACC rebasing it from 4.8 release of yacc from FreeBSD (a byacc derivative).