9base-yacc

YACC(1)                     General Commands Manual                    YACC(1)



NAME
       yacc - yet another compiler-compiler

SYNOPSIS
       yacc [ option ...  ] grammar

DESCRIPTION
       Yacc converts a context-free grammar and translation code into a set of
       tables for an LR(1) parser and translator.  The grammar may be
       ambiguous; specified precedence rules are used to break ambiguities.

       The output file, y.tab.c, must be compiled by the C compiler to produce
       a program This program must be loaded with a lexical analyzer function,
       yylex(void) (often generated by lex(1)), with a main(int argc, char
       *argv[]) program, and with an error handling routine, yyerror(char*).

       The options are

       -o output  Direct output to the specified file instead of y.tab.c.

       -Dn        Create file y.debug, containing diagnostic messages.  To
                  incorporate them in the parser, compile it with preprocessor
                  symbol yydebug defined.  The amount of diagnostic output
                  from the parser is regulated by value n.  The value 0
                  reports errors; 1 reports reductions; higher values (up to
                  4) include more information about state transitions.

       -v         Create file y.output, containing a description of the
                  parsing tables and of conflicts arising from ambiguities in
                  the grammar.

       -d         Create file y.tab.h, containing #define statements that
                  associate yacc-assigned `token codes' with user-declared
                  `token names'.  Include it in source files other than
                  y.tab.c to give access to the token codes.

       -s stem    Change the prefix of the file names y.tab.c, y.tab.h,
                  y.debug, and y.output to stem.

       -S         Write a parser that uses Stdio instead of the print routines
                  in libc.

       -l         Disable #line directives in the generated parser.

       -a         Generate a parser that takes an argument of type Yyarg and
                  passes this argument to each invocation of the lexer
                  function, yylex.  Yyarg contains per-instance state and a
                  single user-visible member, arg, of type void*.

       The specification of yacc itself is essentially the same as the UNIX
       version described in the references mentioned below.  Besides the -D
       option, the main relevant differences are:

              The interface to the C environment is by default through
              <libc.h> rather than <stdio.h>; the -S option reverses this.

              The parser accepts UTF input text (see utf(7)), which has a
              couple of effects.  First, the return value of yylex() no longer
              fits in a short; second, the starting value for non-terminals is
              now 0xE000 rather than 257.

              The generated parser can be recursive: actions can call yyparse,
              for example to implement a sort of #include statement in an
              interpreter.

              Finally, some undocumented inner workings of the parser have
              been changed, which may affect programs that know too much about
              its structure.

FILES
       y.output

       y.tab.c

       y.tab.h

       y.debug

       y.tmp.*
              temporary file

       y.acts.*
              temporary file

       /lib/yaccpar
              parser prototype

       /lib/yaccpars
              parser prototype using stdio

SOURCE
       /src/cmd/yacc.c

SEE ALSO
       lex(1)
       S. C. Johnson and R. Sethi, ``Yacc: A parser generator'', Unix Research
       System Programmer's Manual, Tenth Edition, Volume 2
       B. W. Kernighan and Rob Pike, The UNIX Programming Environment,
       Prentice Hall, 1984

BUGS
       The parser may not have full information when it writes to y.debug so
       that the names of the tokens returned by may be missing.



                                                                       YACC(1)