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yacc(1) [v7 man page]

YACC(1) 						      General Commands Manual							   YACC(1)

NAME
yacc - yet another compiler-compiler SYNOPSIS
yacc [ -vd ] grammar DESCRIPTION
Yacc converts a context-free grammar into a set of tables for a simple automaton which 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. These routines must be supplied by the user; Lex(1) is useful for creating lexical analyzers usable by yacc. If the -v flag is given, the file y.output is prepared, which contains a description of the parsing tables and a report on conflicts gener- ated by ambiguities in the grammar. If the -d flag is used, 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. FILES
y.output y.tab.c y.tab.h defines for token names yacc.tmp, yacc.acts temporary files /usr/lib/yaccpar parser prototype for C programs /lib/liby.a library with default `main' and `yyerror' SEE ALSO
lex(1) LR Parsing by A. V. Aho and S. C. Johnson, Computing Surveys, June, 1974. YACC - Yet Another Compiler Compiler by S. C. Johnson. DIAGNOSTICS
The number of reduce-reduce and shift-reduce conflicts is reported on the standard 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. YACC(1)

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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. -l Disable #line directives in the generated parser. -a Generate a parser that takes an argument of type Yyarg and passes this argument to each invocation of the lexer function, yylex. Yyarg contains per-instance state and a single user-visible member, arg, of type void*. 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(7)), 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 /lib/yaccpar parser prototype /lib/yaccpars parser prototype using stdio SOURCE
/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)

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