On 27 Aug 2013, at 08:33, Niklas Hambüchen wrote:
@Malcolm, would you mind a change towards throwing an exception that is different from error so that it can be easily caught, or even better, a change from
runCpphs :: ... -> IO String
to
runCpphs :: ... -> IO (Either String String)
or similar?
Have you tried simply wrapping the call to runCpphs in a "catch"? Something like safeRunCpphs :: ... -> IO (Either String String) safeRunCpphs foo = fmap Right (runCpphs foo) `catch` (\(UserError s)-> Left s
If an exception based interface is kept, it would be nice to add some haddock to `runCpphs`; not knowing about the existence of #error, it is easy to assume that the IO is only used for accessing the FilePath passed in.
The IO is used also for reading #include'd files, of course. I'd be happy to add some extra documentation making the behaviour on #error clearer, if you can suggest some text that would have helped you. Regards, Malcolm