yacc(1)                                                   yacc(1)



     NAME
          yacc - yet another compiler-compiler

     SYNOPSIS
          yacc [-d] [-l] [-t] [-v] grammar

     DESCRIPTION
          yacc converts a context-free grammar into a set of tables
          for a simple automaton which executes an lr(1) parsing algo-
          rithm.  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 yyparse.  This program must be loaded
          with the lexical analyzer program, yylex, as well as main
          and yyerror, an error handling routine.  These routines must
          be supplied by the user; lex(1) is useful for creating lexi-
          cal analyzers usable by yacc.

          If the -v flag is given, the file y.output is prepared,
          which contains a description of the parsing tables and a re-
          port on conflicts generated by ambiguities in the grammar.

          If the -d flag is used, the file y.tab.h is generated with
          the #define statements that associate the yacc-assigned
          ``token codes'' with the user-declared ``token names'' This
          allows source files other than y.tab.c to access the token
          codes.

          If the -l flag is given, the code produced in y.tab.c will
          not contain any #line constructs.  This should only be used
          after the grammar and the associated actions are fully de-
          bugged.

          Runtime debugging code is always generated in y.tab.c under
          conditional compilation control.  By default, this code is
          not included when y.tab.c is compiled.  However, when yacc's
          -t flag option is used, this debugging code will be compiled
          by default.  Independent of whether the -t flag option was
          used, the runtime debugging code is under the control of
          YYDEBUG, a pre-processor symbol.  If YYDEBUG has a nonzero
          value, then the debugging code is included.  If its value is
          zero, then the code will not be included.  The size and exe-
          cution time of a program produced without the runtime debug-
          ging code will be smaller and slightly faster.

     EXAMPLES
               yacc file1.y

          invokes yacc to process file file1.y in yacc-format.





     April, 1990                                                     1

     yacc(1)                                                   yacc(1)



     FILES
          /bin/yacc
          y.output
          y.tab.c
          y.tab.h
          yacc.tmp,yacc.debug,yacc.acts (temporary files)
          /usr/lib/yaccpar

     SEE ALSO
          lex(1), malloc(3X).
          ``yacc Refrence'' in A/UX Programming Languages and Tools,
          Volume 2.

     DIAGNOSTICS
          The number of reduce-reduce and shift-reduce conflicts is
          reported on the standard error output; a more detailed re-
          port is found in the y.output file.  Similarly, if some
          rules are not reachable from the start symbol, this is also
          reported.

     BUGS
          Because file names are fixed, at most one yacc process can
          be active in a given directory at a time.
































     2                                                     April, 1990