Edit File: NEW_FEATURES
The -r option has been implemented. The -r option tells Yacc to put the read-only tables in y.tab.c and the code and variables in y.code.c. Keith Bostic asked for this option so that :yyfix could be eliminated. The -l and -t options have been implemented. The -l option tells Yacc not to include #line directives in the code it produces. The -t option causes debugging code to be included in the compiled parser. The code for error recovery has been changed to implement the same algorithm as AT&T Yacc. There will still be differences in the way error recovery works because AT&T Yacc uses more default reductions than Berkeley Yacc. The environment variable TMPDIR determines the directory where temporary files will be created. If TMPDIR is defined, temporary files will be created in the directory whose pathname is the value of TMPDIR. By default, temporary files are created in /tmp. The keywords are now case-insensitive. For example, %nonassoc, %NONASSOC, %NonAssoc, and %nOnAsSoC are all equivalent. Commas and semicolons that are not part of C code are treated as commentary. Line-end comments, as in BCPL, are permitted. Line-end comments begin with // and end at the next end-of-line. Line-end comments are permitted in C code; they are converted to C comments on output. The form of y.output files has been changed to look more like those produced by AT&T Yacc. A new kind of declaration has been added. The form of the declaration is %ident string where string is a sequence of characters begining with a double quote and ending with either a double quote or the next end-of-line, whichever comes first. The declaration will cause a #ident directive to be written near the start of the output file. If a parser has been compiled with debugging code, that code can be enabled by setting an environment variable. If the environment variable YYDEBUG is set to 0, debugging output is suppressed. If it is set to 1, debugging output is written to standard output.