Re: [Haskell-cafe] Inverting a Monad

On Feb 6, 2008 1:49 PM, Lutz Donnerhacke wrote:

inv m = if m == mzero then return () else mzero `asTypeOf` m

Interesting!

:t inv inv :: (MonadPlus m, Eq (m ())) => m () -> m ()

The 'Eq' constraint on 'm ()' is a bit problemetic I think in case 'm' is a function like a 'State'. Thanks, Bas