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1.1 root 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: .RS
50: .TP
51: 0
52: Report errors.
53: .TP
54: 1
55: Also report reductions.
56: .TP
57: 2
58: Also report the name of each token returned by
59: .LR yylex .
60: .RE
61: .TP
62: .B -v
63: Create file
64: .BR y.output ,
65: containing a description of the parsing tables and of
66: conflicts arising from ambiguities in the grammar.
67: .TP
68: .B -d
69: Create file
70: .BR y.tab.h ,
71: containing
72: .B #define
73: statements that associate
74: .IR yacc -assigned
75: `token codes' with user-declared `token names'.
76: Include it in source files other than
77: .B y.tab.c
78: to give access to the token codes.
79: .TP
80: .BI -s " stem
81: Change the prefix
82: .L y
83: of the file names
84: .BR y.tab.c ,
85: .BR y.tab.h ,
86: .BR y.debug ,
87: and
88: .B y.output
89: to
90: .IR stem .
91: .TP
92: .B -S
93: Write a parser that uses
94: Stdio
95: instead of the
96: .B print
97: routines in libc.
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 (6)),
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 257.
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 structure.
134: .SH FILES
135: .TF /sys/lib/yaccpars
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 /sys/lib/yaccpar
152: parser prototype
153: .TP
154: .B /sys/lib/yaccpars
155: parser prototype using stdio
156: .SH SOURCE
157: .B /sys/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.
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