Hi, I've implemented replacements for readsPrec for Int and Integer in a module called Compat (in my darcs repository [1]) and measured their performance. There's some overhead when compared to the plain versions. For Integer, it's about 30% for single digit numbers, going down to about 10% at 10 digits, and about 1.3% at 100. It's still a big win over the existing instances at a small loss in compatibility to Haskell 98. As far as I can make out, the only difference is that it fails to diverge in some cases where reads would diverge (see my initial mail for an example.) I've also received a question from Ketil Malde off list, asking (in reply to Neil Mitchell) what the advantages would be of having this in base. Personally I think it should go into base if we can agree on replacing existing code (the Read instances or something in Numeric or maybe both). This would have the advantage of making quite a few programs more efficient just by recompiling them. If we can't agree on that, the code will be made available as an extra module but I wouldn't see any advantage at having it in base. Having it distributed with ghc would have some advantages (mainly convenience for users and a slightly better chance of avoiding forks). In other news, darcs send will now send the patches to me - in case anyone has any. regards, Bertram [1] I'll say again that browsing directly doesn't work, darcs is fine though, get the code with darcs get http://int-e.home.tlink.de/haskell/readinteger