yacc(1)                    DG/UX 4.30                     yacc(1)



     NAME
          yacc - yet another compiler-compiler

     SYNOPSIS
          yacc [ -vdlt ] grammar

     DESCRIPTION
          Yacc converts a context-free grammar into a set of tables
          for a simple automaton that executes an LR(1) parsing
          algorithm.  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.  The user must
          supply these routines.  Lex(1) is useful for creating
          lexical analyzers usable by yacc.

          If you use -v flag, the file y.output is prepared.  It
          contains a description of the parsing tables and a report on
          conflicts generated by ambiguities in the grammar.

          If you use the -d flag, 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 you use the -l flag, the code produced in y.tab.c will
          not contain any #line constructs.  Use this after the
          grammar and the associated actions are fully debugged.

          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 option is used, this debugging code will be compiled by
          default.  With or without -t option, the runtime debugging
          code is under the control of YYDEBUG, a pre-processor
          symbol.  If YYDEBUG has a non-zero value, then the debugging
          code is included.  If its value is zero, then the code will
          not be included.  The size and execution time of a program
          produced without the runtime debugging code will be smaller
          and slightly faster.

     FILES
          y.output
          y.tab.c
          y.tab.h             Defines for token names
          yacc.tmp,
          yacc.debug, yacc.acts    Temporary files

     SEE ALSO



     Licensed material--property of copyright holder(s)         Page 1

     yacc(1)                    DG/UX 4.30                     yacc(1)



          lex(1).
          "Yacc-Yet Another Compiler Compiler" in Using DG/UX System
          Programming Tools.

     DIAGNOSTICS
          The number of reduce-reduce and shift-reduce conflicts is
          reported on the standard error output; a more detailed
          report 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.









































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