Last Update Time-stamp: "97/08/27 08:12:43 zdu"

Zyacc Homepage

Zyacc provides the following enhancements:

• Supports inherited attributes which can be uniquely evaluated in a left-to-right parse.
• Supports semantic tests which allow the outcome of runtime semantic tests to affect parsing decisions.
• Permits remote interactive debugging of generated parsers either by using a textual interface or by using a java-based GUI. The debugger allows the setting of breakpoints on any grammar symbol and selective display of the current parser state.
• Allows named attribute variables which make maintaining grammars easier.
• Can generate its parser description files in HTML which can then be viewed using any Web browser (Zyacc Options).
• Provides a %look directive to check (at parser construction time) whether a reduction requires lookahead.
• Allows multiple start nonterminals and allows a call to the parsing function to be made for a particular start nonterminal.
• It is possible to avoid having types which are only used in describing nonterminal semantics written into the generated `.h' file (Data Types of Semantic Values).
• Allows multiple-character quoted literal tokens.
• Allows command-line options to be specified from within the parser file.

You can view a live demonstration of the GUI debugger, or browse the zyacc manual (which is derived from the Bison manual).

The distribution comes with a Prolog frontend which illustrates the use of semantic predicates to handle Prolog's dynamic operators. You can view the zyacc parser file, the associated lex scanner and its interface, a file which tracks current operators and its interface, and some implementation notes.

You can also look at the use of zyacc to build a C-frontend for a source-to-source profiling tool zprof. The use of semantic predicates enables a clean solution to the problem of parsing typedef-name's in C.

If you are interested, you can view a Java applet which demonstrates different parsing algorithms: recursive-descent, LL(1) table-driven parsing and shift-reduce parsing. The GUI to the zyacc debugger is built using some of the same Java classes.

You can download the full distribution including all documentation from zyacc-1.03.tar.gz (1119423 bytes) If you have a slow network connection, a subset distribution is in zyacc-1.03-min-doc.tar.gz ( 631962 bytes) This is the full distribution minus the automatically generated documentation. To build the full documentation from the subset distribution, you will need TeX, texinfo, dvips and texi2html.

If you do not need any of the above features, you are probably better off using GNU's bison which is almost definitely more stable. Also if LALR parsing is not your cup of tea, you should check out a LL(k) parser generator PCCTS.

Other projects.

Feedback: Please email any feedback to zdu@acm.org.