Provided by: byacc_20140101-1_amd64 bug


       Yacc - an LALR(1) parser generator


       yacc [ -dgilrtv ] [ -b file_prefix ] [ -p symbol_prefix ] filename


       Yacc  reads the grammar specification in the file filename and generates an LALR(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 following options are available:

       -b file_prefix
            The -b option changes the prefix prepended to the output file  names  to  the  string
            denoted by file_prefix.  The default prefix is the character y.

       -d   The  -d  option  causes the header file to be written.  It contains #define's
            for the token identifiers.

       -g   The -g option causes a graphical description of the generated LALR(1)  parser  to  be
            written to the file in graphviz format, ready to be processed by dot(1).

       -i   The  -i option causes a supplementary header file to be written.  It contains
            extern declarations and supplementary #define's as needed  to  map  the  conventional
            yacc  yy-prefixed  names to whatever the -p option may specify.  The code file, e.g.,
   is modified to #include this file as well  as  the  file,  enforcing
            consistent usage of the symbols defined in those files.

            The  supplementary  header  file makes it simpler to separate compilation of lex- and

       -l   If the -l option is not specified, yacc will 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 -l option is specified, yacc will  not  insert  the
            #line directives.  #line directives specified by the user will be retained.

       -o output_file
            specify  the  filename  for the parser file.  If this option is not given, the output
            filename is the file prefix concatenated with the file suffix, e.g.,   This
            overrides the -p option.

       -p symbol_prefix
            The  -p  option  changes the prefix prepended to yacc-generated symbols to the string
            denoted by symbol_prefix.  The default prefix is the string yy.

       -P   create a reentrant parser, e.g., “%pure-parser”.

       -r   The -r option causes yacc to produce separate files for code and  tables.   The  code
            file is named y.code.c, and the tables file is named  The prefix “y.” can be
            overridden using the -b option.

       -s   suppress “#define” statements generated for string literals in a “%token”  statement,
            to more closely match original yacc behavior.

            Normally when yacc sees a line such as

                %token OP_ADD "ADD"

            it notices that the quoted “ADD” is a valid C identifier, and generates a #define not
            only for OP_ADD, but for ADD as well, e.g.,

                #define OP_ADD 257
                #define ADD 258

            The original yacc does not generate the second “#define”.  The -s  option  suppresses
            this “#define”.

            POSIX  (IEEE  1003.1  2004)  documents  only  names  and numbers for “%token”, though
            original yacc and bison also accept string literals.

       -t   The -t option changes the preprocessor directives generated by yacc so that debugging
            statements will be incorporated in the compiled code.

       -v   The  -v  option  causes  a  human-readable  description of the generated parser to be
            written to the file y.output.

       -V   print the version number to the standard output.

       -y   yacc ignores this option, which bison supports for ostensible POSIX compatibility.


       yacc provides some extensions for compatibility with bison and  other  implementations  of

        %expect number
              tell yacc the expected number of shift/reduce conflicts.  That makes it only report
              the number if it differs.

        %expect-rr number
              tell yacc the expected number of  reduce/reduce  conflicts.   That  makes  it  only
              report the number if it differs.  This is (unlike bison) allowable in LALR parsers.

        %lex-param { argument-declaration }
              By  default, the lexer accepts no parameters, e.g., yylex().  Use this directive to
              add parameter declarations for your customized lexer.

        %parse-param { argument-declaration }
              By default, the parser accepts no parameters, e.g., yyparse().  Use this  directive
              to add parameter declarations for your customized parser.

              Most  variables  (other than yydebug and yynerrs) are allocated on the stack within
              yyparse, making the parser reasonably reentrant.

              Make the parser's names for tokens available in the yytname array.   However,  yacc
              does not predefine “$end”, “$error” or “$undefined” in this array.


       According to Robert Corbett,

               Berkeley Yacc is an LALR(1) parser generator.  Berkeley Yacc has been made
           as compatible as possible with AT&T Yacc.  Berkeley Yacc can accept any input
           specification that conforms to the AT&T Yacc documentation.  Specifications
           that take advantage of undocumented features of AT&T Yacc will probably be

       The rationale in


       documents some features of AT&T yacc which are no longer required for POSIX compliance.

       That  said, you may be interested in reusing grammary files with some other implementation
       which is not strictly compatible with AT&T yacc.  For instance, there is bison.  Here  are
       a few differences:

       ·   Yacc  accepts  an  equals  mark preceding the left curly brace of an action (as in the
           original grammar file ftp.y):

                    |    STAT CRLF
                         = {

       ·   Yacc and bison emit code in different order, and in  particular  bison  makes  forward
           reference  to  common  functions  such as yylex, yyparse and yyerror without providing

       ·   Bison's support for “%expect” is broken in more than one release.   For  best  results
           using bison, delete that directive.

       ·   Bison  has  no  equivalent  for  some  of  yacc's  commmand-line  options,  relying on
           directives embedded in the grammar file.

       ·   Bison's “-y” option does not affect bison's lack of support for features of AT&T  yacc
           which were deemed obsolescent.


       If  there  are  rules  that  are  never  reduced,  the number of such rules is reported on
       standard error.  If there are any LALR(1) conflicts, the number of conflicts  is  reported
       on standard error.