On Aug 8, 2007, at 3:47 PM, Nick Maclaren wrote: > Firstly, things like backreferences are an absolute no-no. They > are not regular, and REs with them in cannot be converted to DFAs. > That could be 'solved' by a parser that kicked out such constructions, > but it would get screams from many users.
People keep saying things like this as if GNU grep and tcl's regular expression matchers didn't exist. See http://www.tcl.tk/man/tcl8.5/TclCmd/re_syntax.htm for example. time python -c 'import re; print re.match("("+"a?"*26+"a"*26+")b\\1", "a"*26+"b"+"a"*26).group(0)' aaaaaaaaaaaaaaaaaaaaaaaaaabaaaaaaaaaaaaaaaaaaaaaaaaaa real 0m5.913s user 0m5.905s sys 0m0.006s time echo 'aaaaaaaaaaaaaaaaaaaaaaaaaabaaaaaaaaaaaaaaaaaaaaaaaaaa' | grep -E '(a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a? aaaaaaaaaaaaaaaaaaaaaaaaaa)b\1' aaaaaaaaaaaaaaaaaaaaaaaaaabaaaaaaaaaaaaaaaaaaaaaaaaaa real 0m0.002s user 0m0.002s sys 0m0.000s James _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
