Re: [9fans] empty *

[Anthony Martin]

% sed -n 20,32p /sys/src/cmd/grep/grep.y
prog:   /* empty */
        {
                yyerror("empty pattern");
        }
|       expr newlines
        {
                $$.beg = ral(Tend);
                $$.end = $$.beg;
                $$ = re2cat(re2star(re2or(re2char(0x00, '\n'-1), 
re2char('\n'+1, 0xff))), $$);
                $$ = re2cat($1, $$);
                $$ = re2cat(re2star(re2char(0x00, 0xff)), $$);
                topre = $$;
        }
%

The above code sets up the initial state
machine including the pattern passed on
the command line, $1.

This combined with the fact that multiple
"stars" are coalesced causes the weirdness
you're seeing.

  Anthony