CError/IOError issues

[Manuel M. T. Chakravarty]

qrczak@knm.org.pl (Marcin 'Qrczak' Kowalczyk) wrote,

> This mess should be cleared out. IMHO ghc should store the error
> description in IOException separately from the filename. Haskell98
> doesn't provide an interface to extract the location (function name
> where the error occurred) from an IOError, so it would be used only
> for showing the IOError. fail should use UserErrors, ioeGetErrorString
> and friends should understand UserErrors - or UserErrors should be
> put with other IOErrors again?

Sounds sensible to me.

> Perhaps CError should provide a function to build an IOError value
> (not throwing it) from the function name, errno number, Maybe Handle
> and Maybe FilePath. Plus throwErrno as a quick variant which takes the
> function name from the parameter, takes the errno number from the errno
> variable, sets other two components to Nothing and throws the error.
> throwCError would be gone.

I was wondering about that, too.  But I wasn't sure whether
such functionality is really needed.  However, it might be a
bit more inline with the interface provided by the IO monad,
where you have `userError' to build an `IOError' and
`ioError' to throw it.  Opinions?

Cheers,
Manuel