On 1/3/11 7:22 PM, Isaac Dupree wrote:
On 01/03/11 17:30, Bas van Dijk wrote:
... The patch for base makes a few changes:
1) Make Applicative a superclass of Monad. So the new hierarchy becomes:
2) Make 'join' a method of Monad. ... class Applicative m => Monad m where ... (>>) :: forall a b. m a -> m b -> m b (>>) = (*>)
The former/current default definition of (>>) was based on (>>=), not (*>) (which if itself is undefined, itself defaults to (fmap (const id) a <*> b). That's a change.
Yes, that is a change.
You also added defaults for most of the Monad methods, though they're obvious and I approve. The (>>) default might have worse performance than the previous default though?
Nope. Since (*>) is a class method it can be given the most efficient implementation possible for the given type. Since (>>) is logically the same function, then it should default to (*>) so that the efficient implementation doesn't need to be duplicated. In the event that neither is defined explicitly, then they will both default to the same definition as pre-patch. -- Live well, ~wren