Re: Add Applicative instances for MTL types

On Wed, Jan 14, 2009 at 7:56 PM, David Menendez wrote:

No, in your definition, the effects of the transformed applicative functor are evaluated regardless of the error condition.

Try this code:

runState (runErrorT (throwError "!" <*> put False)) True

The first definition of <*> returns (Left "!", True). The second returns (Left "!", False).

I see it now. Thanks for correcting me. Then we should consider the first patch by Spencer Janssen again which satisfies these laws: pure = return (<*>) = ap Thanks, Bas