Hi, I have the following code in my MissingH tree. I think it would make a good addition to Text.Regex in fptools. Is this the right place to ask? -- John {- | Replaces every occurance of the given regexp with the replacement string. In the replacement string, @\"\\1\"@ refers to the first substring; @\"\\2\"@ to the second, etc; and @\"\\0\"@ to the entire match. @\"\\\\\\\\\"@ will insert a literal backslash. -} subRe :: Regex -- ^ Search pattern -> String -- ^ Input string -> String -- ^ Replacement text -> String -- ^ Output string subRe _ "" _ = "" subRe regexp inp repl = let bre = mkRegex "\\\\(\\\\||[0-9]+)" lookup _ [] _ = [] lookup [] _ _ = [] lookup match repl groups = case matchRegexAll bre repl of Nothing -> repl Just (lead, _, trail, bgroups) -> let newval = if (head bgroups) == "\\" then "\\" else let index = (read (head bgroups)) - 1 in if index == -1 then match else groups !! index in lead ++ newval ++ lookup match trail groups in case matchRegexAll regexp inp of Nothing -> inp Just (lead, match, trail, groups) -> lead ++ lookup match repl groups ++ (subRe regexp trail repl) {- | Splits a string based on a regular expression. The regular expression should identify one delimiter. -} splitRe :: Regex -> String -> [String] splitRe _ [] = [] splitRe delim str = case matchRegexAll delim str of Nothing -> [str] Just (firstline, _, remainder, _) -> if remainder == "" then firstline : [] : [] else firstline : splitRe delim remainder