Applicative instance for ST

Ross Paterson ross at
Fri Oct 29 19:05:49 EDT 2010

On Fri, Oct 29, 2010 at 04:11:07PM -0400, Daniel Peebles wrote:
> Strangely enough, ST has a Functor and a Monad instance, but no Applicative
> instance (I guess it was pre-Applicative). I propose to add one. It doesn't
> seem very controversial, but I guess a normal discussion period for these
> proposals is two weeks? 

Indeed everything with a Monad instance should have a matching Applicative
instance.  You'll need one for Control.Monad.ST.Lazy(ST) too.

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