[Haskell-cafe] Text.Regex.Base throws exceptions with makeRegexOptsM

Hi folks, I'm using Text.Regex.Base with the TDFA and PCRE backends. I want to compile regular expressions first and make sure the patterns were actually valid, so I used makeRegexOptsM, which indicates a bad regular expression by calling fail. That allows you to use makeRegexOptsM with Maybe or

Re: [Haskell-cafe] Text.Regex.Base throws exceptions with makeRegexOptsM

On Thursday 29 December 2011, 23:52:46, Omari Norman wrote: Hi folks, I'm using Text.Regex.Base with the TDFA and PCRE backends. I want to compile regular expressions first and make sure the patterns were actually valid, so I used makeRegexOptsM, which indicates a bad regular expression by

Re: [Haskell-cafe] Text.Regex.Base throws exceptions with makeRegexOptsM

On Fri, Dec 30, 2011 at 01:24:02AM +0100, Daniel Fischer wrote: For Either, there used to be instance Error e = Monad (Either e) where ... fail s = Left (strMsg s) in mtl's Control.Monad.error, and all was fine if one used the regex functions with e.g. (Either String) as the

Re: [Haskell-cafe] Text.Regex.Base throws exceptions with makeRegexOptsM

On Fri, Dec 30, 2011 at 1:24 PM, Daniel Fischer daniel.is.fisc...@googlemail.com wrote: On Thursday 29 December 2011, 23:52:46, Omari Norman wrote: [...] 'fail' doesn't properly belong in the Monad class, it was added for the purpose of dealing with pattern-match failures, but most monads