> * Paul Eggert <[EMAIL PROTECTED]> [2005-08-20 23:01:23 -0700]:
>
> Sam Steingold <[EMAIL PROTECTED]> writes:
>
>> the latest and greatest gnulib regexp has the following regressions vs
>> the previous (monolithic) version:
>
> Sorry, I didn't understand the notation that you used in
> <http://lists.gnu.org/archive/html/bug-gnulib/2005-08/msg00008.html>.
;; common lisp:
(defun re-test (pattern string)
(mapcar (lambda (match)
(and match (regexp:match-string string match)))
(multiple-value-list
(regexp:regexp-exec (regexp:regexp-compile pattern :extended t)
string))))
this function takes an extended regular expression pattern and a string
and tries to match them, returning a list of substrings of the string
that matched subexpressions of the pattern
Form: (RE-TEST "(^)*" "-")
;; pattern = (^)*
;; string = -
CORRECT: ("" "")
;; the previous (single-file) version returned two matches: for
;; the whole expression and for the first subexpressions, both
;; had length 0
CLISP : ("" NIL)
;; the current (multi-file) version returns just one match -
;; for the whole expression, no matches for the subexpression
;; this is the explanation of how ("" "") is different from ("" NIL)
Differ at position 1: "" vs NIL
CORRECT: ("")
CLISP : (NIL)
> I tried to reproduce the problems by writing a C program (enclosed
> below) and it seems to me that the gnulib regexp is correct in all
> these test cases. Perhaps the old regexp was broken.
frankly I don't know and don't care whether the old or new was / is broken.
All I care about is consistency.
May I suggest that you add regression testing to the parts of gnulib
that exhibit non-trivial functionality, like regex?
Does glibc come with regression tests?
Do those tests cover regex?
Consistency over time - or at least explicitly documented changes -
is quite important (IMNSHO).
Actually, the careful examination of the examples appears to indicate
that the previous behavior was "more" correct.
Specifically, the first 3 of the 6 regressions are clearly bugs in the
current regex implementation while the last 3 are acceptable - but
undesirable - variations.
--
Sam Steingold (http://www.podval.org/~sds) running w2k
<http://www.iris.org.il> <http://www.palestinefacts.org/>
<http://www.jihadwatch.org/> <http://www.openvotingconsortium.org/>
Never succeed from the first try - if you do, nobody will think it was hard.
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