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 func-
       tion,  yylex(void)  (often  generated  by  lex(1)),  with a main(int argc, char *argv[]) program, and with an error handling routine, yyer-
       ror(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.

       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(6)), 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 inter-
	      preter.

	      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

       /sys/lib/yaccpar
	      parser prototype

       /sys/lib/yaccpars
	      parser prototype using stdio

SOURCE

       /sys/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)