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 .PP
90 The specification of
91 .I yacc
92 itself is essentially the same as the UNIX version
93 described in the references mentioned below.
94 Besides the
95 .B -D
96 option, the main relevant differences are:
97 .IP
98 The interface to the C environment is by default through
99 .B <libc.h>
100 rather than
101 .BR <stdio.h> ;
102 the
103 .B -S
104 option reverses this.
105 .IP
106 The parser accepts
107 .SM UTF
108 input text (see
109 .IR utf (6)),
110 which has a couple of effects.
111 First, the return value of
112 .B yylex()
113 no longer fits in a
114 .BR short ;
115 second, the starting value for non-terminals is now 0xE000 rather than 257.
116 .IP
117 The generated parser can be recursive: actions can call
118 .IR yyparse ,
119 for example to implement a sort of
120 .B #include
121 statement in an interpreter.
122 .IP
123 Finally, some undocumented inner workings of the parser have been
124 changed, which may affect programs that know too much about its structure.
125 .SH FILES
126 .TF y.debug.xxxxx
127 .TP
128 .B y.output
129 .TP
130 .B y.tab.c
131 .TP
132 .B y.tab.h
133 .TP
134 .B y.debug
135 .TP
136 .B y.tmp.*
137 temporary file
138 .TP
139 .B y.acts.*
140 temporary file
141 .TP
142 .B /usr/local/plan9/lib/yaccpar
143 parser prototype
144 .TP
145 .B /usr/local/plan9/lib/yaccpars
146 parser prototype using stdio
147 .SH SOURCE
148 .B /usr/local/plan9/src/cmd/yacc.c
149 .SH "SEE ALSO"
150 .IR lex (1)
151 .br
152 S. C. Johnson and R. Sethi,
153 ``Yacc: A parser generator'',
154 .I
155 Unix Research System Programmer's Manual,
156 Tenth Edition, Volume 2
157 .br
158 B. W. Kernighan and Rob Pike,
159 .I
160 The UNIX Programming Environment,
161 Prentice Hall, 1984
162 .SH BUGS
163 The parser may not have full information when it writes to
164 .B y.debug
165 so that the names of the tokens returned by
166 .L yylex
167 may be missing.