The Free On-line Dictionary of Computing (30 December 2018):

ayacc

    A Yacc-like parser generator developed at
   the Irvine Research Unit in Software around 1994.  ayacc was
   written in Ada and produces Ada output.  aflex was the
   associated lexical analyser.

   (http://www.ics.uci.edu/~arcadia/Aflex-Ayacc/aflex-ayacc.html)

   (2018-01-13)