[Haskell-cafe] Inverting a Monad

[Bas van Dijk]

On Feb 6, 2008 1:49 PM, Lutz Donnerhacke <lutz at iks-jena.de> 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