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	yacc.1 - 9base - revived minimalist port of Plan 9 userland to Unix
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	yacc.1 (3556B)
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	1 .TH YACC 1
	2 .SH NAME
	3 yacc \- yet another compiler-compiler
	4 .SH SYNOPSIS
	5 .B yacc
	6 [
	7 .I option ...
	8 ]
	9 .I grammar
	10 .SH DESCRIPTION
	11 .I Yacc
	12 converts a context-free grammar and translation code
	13 into a set of
	14 tables for an LR(1) parser and translator.
	15 The grammar may be ambiguous;
	16 specified precedence rules are used to break ambiguities.
	17 .PP
	18 The output file,
	19 .BR y.tab.c ,
	20 must be compiled by the C compiler
	21 to produce a program
	22 .LR yyparse .
	23 This program must be loaded with a lexical analyzer function,
	24 .B yylex(void)
	25 (often generated by
	26 .IR lex (1)),
	27 with a
	28 .B main(int argc, char *argv[])
	29 program, and with an error handling routine,
	30 .BR yyerror(char*) .
	31 .PP
	32 The options are
	33 .TP "\w'\fL-o \fIoutput\fLXX'u"
	34 .BI -o " output
	35 Direct output to the specified file instead of
	36 .BR y.tab.c .
	37 .TP
	38 .BI -D n
	39 Create file
	40 .BR y.debug ,
	41 containing diagnostic messages.
	42 To incorporate them in the parser, compile it with preprocessor symbol
	43 .B yydebug
	44 defined.
	45 The amount of
	46 diagnostic output from the parser is regulated by
	47 value
	48 .IR n .
	49 The value 0 reports errors; 1 reports reductions;
	50 higher values (up to 4) include more information about
	51 state transitions.
	52 .TP
	53 .B -v
	54 Create file
	55 .BR y.output ,
	56 containing a description of the parsing tables and of
	57 conflicts arising from ambiguities in the grammar.
	58 .TP
	59 .B -d
	60 Create file
	61 .BR y.tab.h ,
	62 containing
	63 .B #define
	64 statements that associate
	65 .IR yacc -assigned
	66 `token codes' with user-declared `token names'.
	67 Include it in source files other than
	68 .B y.tab.c
	69 to give access to the token codes.
	70 .TP
	71 .BI -s " stem
	72 Change the prefix
	73 .L y
	74 of the file names
	75 .BR y.tab.c ,
	76 .BR y.tab.h ,
	77 .BR y.debug ,
	78 and
	79 .B y.output
	80 to
	81 .IR stem .
	82 .TP
	83 .B -S
	84 Write a parser that uses
	85 Stdio
	86 instead of the
	87 .B print
	88 routines in libc.
	89 .TP
	90 .BI -l
	91 Disable #line directives in the generated parser.
	92 .TP
	93 .BI -a
	94 Generate a parser that takes an argument of type Yyarg
	95 and passes this argument to each invocation of the lexer
	96 function, yylex. Yyarg contains per-instance state
	97 and a single user-visible member, arg, of type void*.
	98 .PP
	99 The specification of
	100 .I yacc
	101 itself is essentially the same as the UNIX version
	102 described in the references mentioned below.
	103 Besides the
	104 .B -D
	105 option, the main relevant differences are:
	106 .IP
	107 The interface to the C environment is by default through
	108 .B <libc.h>
	109 rather than
	110 .BR <stdio.h> ;
	111 the
	112 .B -S
	113 option reverses this.
	114 .IP
	115 The parser accepts
	116 .SM UTF
	117 input text (see
	118 .IR utf (7)),
	119 which has a couple of effects.
	120 First, the return value of
	121 .B yylex()
	122 no longer fits in a
	123 .BR short ;
	124 second, the starting value for non-terminals is now 0xE000 rather than 2…
	125 .IP
	126 The generated parser can be recursive: actions can call
	127 .IR yyparse ,
	128 for example to implement a sort of
	129 .B #include
	130 statement in an interpreter.
	131 .IP
	132 Finally, some undocumented inner workings of the parser have been
	133 changed, which may affect programs that know too much about its structur…
	134 .SH FILES
	135 .TF y.debug.xxxxx
	136 .TP
	137 .B y.output
	138 .TP
	139 .B y.tab.c
	140 .TP
	141 .B y.tab.h
	142 .TP
	143 .B y.debug
	144 .TP
	145 .B y.tmp.*
	146 temporary file
	147 .TP
	148 .B y.acts.*
	149 temporary file
	150 .TP
	151 .B \*9/lib/yaccpar
	152 parser prototype
	153 .TP
	154 .B \*9/lib/yaccpars
	155 parser prototype using stdio
	156 .SH SOURCE
	157 .B \*9/src/cmd/yacc.c
	158 .SH "SEE ALSO"
	159 .IR lex (1)
	160 .br
	161 S. C. Johnson and R. Sethi,
	162 ``Yacc: A parser generator'',
	163 .I
	164 Unix Research System Programmer's Manual,
	165 Tenth Edition, Volume 2
	166 .br
	167 B. W. Kernighan and Rob Pike,
	168 .I
	169 The UNIX Programming Environment,
	170 Prentice Hall, 1984
	171 .SH BUGS
	172 The parser may not have full information when it writes to
	173 .B y.debug
	174 so that the names of the tokens returned by
	175 .L yylex
	176 may be missing.