an LALR(1) parser generator
yacc reads the grammar specification in
file and generates an LR(1) parser for it. The parsers
consist of a set of LALR(1) parsing tables and a driver routine written in
the C programming language.
yacc normally writes the
parse tables and the driver routine to the file
The options are as follows:
-boption changes the prefix prepended to the output file names to the string denoted by file_prefix. The default prefix is the character y.
-doption causes the header file y.tab.h to be written.
- If the
-loption is not specified,
yaccwill insert #line directives in the generated code. The #line directives let the C compiler relate errors in the generated code to the user's original code. If the
-loption is specified,
yaccwill not insert the #line directives. #line directives specified by the user will be retained.
-ooption specifies an explicit name for the parser's output file name instead of the default. The names of the other output files are constructed from output_file as described under the
-poption changes the prefix prepended to yacc-generated symbols to the string denoted by symbol_prefix. The default prefix is the string yy.
yaccto produce separate files for code and tables. The code file is named y.code.c, and the tables file is named y.tab.c.
-toption changes the preprocessor directives generated by
yaccso that debugging statements will be incorporated in the compiled code.
-voption causes a human-readable description of the generated parser to be written to the file y.output.
The names of the tables generated by this version of
yacc are “yylhs”,
“yylen”, “yydefred”, “yydgoto”,
“yygindex”, “yytable”, and
“yycheck”. Two additional tables, “yyname” and
“yyrule”, are created if
defined and non-zero.
yacc utility exits 0 on
success, and >0 if an error occurs.
If there are rules that are never reduced, the number of such rules is written to the standard error. If there are any LALR(1) conflicts, the number of conflicts is also written to the standard error.
F. DeRemer and T. J. Pennello, Efficient Computation of LALR(1) Look-Ahead Sets, TOPLAS, Issue 4, Volume 4, pp. 615–649, 1982.
yacc utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
specification, though its presence is optional.
The flags [
-or] are extensions to that
yacc was originally developed at AT&T
by Stephen C. Johnson.
yacc was originally developed
using PCC on a VAX with the intent of being as compatible as possible with
yacc. Much is
owed to the unflagging efforts of Keith Bostic. His badgering kept me
yacc long after I was ready to quit.
yacc is based on the excellent
algorithm for computing LALR(1) lookaheads developed by Tom
Pennello and Frank DeRemer. The algorithm is
described in their almost impenetrable article in TOPLAS (see above).
Finally, much credit must go to those who pointed out deficiencies of earlier releases. Among the most prolific contributors were Benson I. Margulies, Dave Gentzel, Antoine Verheijen, Peter S. Housel, Dale Smith, Ozan Yigit, John Campbell, Bill Sommerfeld, Paul Hilfinger, Gary Bridgewater, Dave Bakken, Dan Lanciani, Richard Sargent, and Parag Patel.
yacc utility was written by