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

Jules Bean writes:

...

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).

Or you could use the monad:

data Perhaps a = Success a | Failure a [Error]

This is just a special case of the writer monad, I think.

It's the same as the writer monad, with redundant encoding of the case when there are no errors. -- __("< Marcin Kowalczyk \__/ qrczak@knm.org.pl ^^ http://qrnik.knm.org.pl/~qrczak/