Re: [Haskell-cafe] How to define instance for type synonym with parameter.

Aren't ErrorT and ReaderT instances of Applicative already? (At least in 'transformers' package?)

what difference between 'mtl' and 'transformers' packages ? 'mtl' goes with Haskell Platform as standard package, so what is the benefit of 'transformers' library ? Thanks, Vasyl