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Ayacc is an Ada parser generator in the style of yacc(1).

The first implementation was written by David Taback and Deepak Tolani at the University of California, Irvine. The last version that was released appeared to be the Ayacc 1.1 released in 1994.

Ayacc was used and improved by P2Ada, the Pascal to Ada translator. This version of Ayacc is derived from the P2Ada ayacc implementation released in August 2010.

This version brings a number of improvements:

  • Ayacc now uses more standard options to configure the code generation
  • The parser was improved to configure the parser stack size and support Ada child packages.
  • The grammar supports the %unit directive to control the Ada child packages
  • It is possible to customize the YYParse procedure and pass some context arguments that are available to the grammar rules.
  • The call to YYLex can be customized with the %lex directive allowing to give some context arguments when calling the lexer.
  • Ayacc can now generate reentrant parsers.

Version 1.4.1 - Feb 2024

  • Fix #7: Update ayacc.gpr: create missing dirs
  • Fix #8: Update clean target in calc example and rename example package

Version 1.4.0 - May 2023

  • Support the Bison %define variable value option to configure the parser generator
  • Support the Bison %code name { ... } directive to insert code verbatim into the output parser
  • Recognize some Bison variables api.pure, api.private, parse.error, parse.stacksize,, parse.params, parse.yyclearin, parse.yyerrok, parse.error
  • New option -S skeleton to allow using an external skeleton file for the parser generator
  • Ayacc templates provide more control for tuning the code generation and they are embedded with Advanced Resource Embedder
  • New option -P to generate a private Ada package for the tokens package
  • Improvement to allow passing parameters to YYParse for the grammar rules
  • New %lex directive to control the call of YYLex function
  • Fix #6: ayacc gets stuck creating an infinitely large file after encountering a comment in an action
  • Reformat code using gnatpp

Version 1.3.0 - Dec 2021

  • New option -C to disable the generation of yyclearin procedure,
  • New option -E to disable the generation of yyerrok procedure,
  • New option -D to write the generated files to the directory specified,
  • New option -k to keep the case of grammar symbols,
  • Fixed various compilation warnings,
  • Generate constants for shift reduce and goto arrays,
  • Better strong typing in the generated state tables,
  • Reduced number of style compilation warnings in generated code




  make install prefix=/usr

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Projects Using Ayacc