On 16.12.2013 18:37, Niklas Hambüchen wrote:
(Fwiw, I've tested attaching such a warning to `fail` in GHC HEAD's libraries/base/GHC/Base.lhs and it seems to work just fine so far... so if there's consensus, we could add that for GHC 7.8)
That sounds great!
And as far as I remember, we will have MonadFail, as Malcolm mentioned, soon.
On 16/12/13 13:54, Andreas Abel wrote
fail :: String -> m a
Fail with a message. This operation is not part of the mathematical definition of a monad, but is invoked on pattern-match failure in a do expression.
This seems to go well with your change.
Above I was just quoting the current documentation. It should be formulated sharper, to say explicitly "do not use `fail' to throw your own errors!" -- Andreas Abel <>< Du bist der geliebte Mensch. Theoretical Computer Science, University of Munich Oettingenstr. 67, D-80538 Munich, GERMANY andreas.abel@ifi.lmu.de http://www2.tcs.ifi.lmu.de/~abel/