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 generated 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

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 (included
in the MachTen Programmer’s Guide).

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.