David Feuer wrote:
+1 on both the goal and the means of reaching it. That said, I suspect the claim that "This has a comparable impact to the AMP" may be overly optimistic.
I want to echo this concern. In fact, the most common way of fixing code after the AMP proposal seems to have been to mechanically add instances instance Functor Foo where fmap = liftM instance Applicative Foo where pure = return (<*>) = ap whenever the compiler complained about a missing Applicative instance for a monad Foo. All those Applicative instances would have to be rewritten under the MRP proposal, and that task is not purely mechanical, since it involves moving existing code, so I'd say that the burden would be higher than after the AMP proposal. How many of those Applicative instances are there in hackage? Cheers, Bertram