Re: [Haskell-cafe] Re: not possible with monad transformers ?

Ben Rudiak-Gould <Benjamin.Rudiak-Gould@cl.cam.ac.uk> writes:

I may be confused, but I don't think it does. It seems like the OP wants a type like

data Perhaps a = Success a | Failure [Error]

When writing a compiler, it makes sense to collect errors as by the writer monad, and not abort anything - producing dummy values instead (except perhaps some fatal errors when it's inconvenient). -- __("< Marcin Kowalczyk \__/ qrczak@knm.org.pl ^^ http://qrnik.knm.org.pl/~qrczak/