FunctorM

[John Meacham]

On Thu, Mar 02, 2006 at 01:10:42PM +0000, Ross Paterson wrote:
> On Thu, Mar 02, 2006 at 05:02:39AM -0800, John Meacham wrote:
> > On Thu, Mar 02, 2006 at 12:41:22PM +0000, Ross Paterson wrote:
> > > I propose to deprecate Data.FunctorM in favour of Data.Traversable:
> > 
> > I have no particular objection, The applicative stuff looks interesting,
> > though I have not explored it too much.
> > 
> > my only request is that we add 'mapM_' and 'sequence_' to the
> > traversable class, there are many monads for which they are vital for
> > controlling space leaks.
> 
> They're in Data.Foldable, though not as class methods:
> 
> http://www.haskell.org/ghc/dist/current/docs/libraries/base/Data-Foldable.html
> 
> e.g. Set is an instance of Foldable but not Traversable.

They should definitly be made class methods somewhere. They usually have
to be custom written for a given datatype and RULES pragmas arn't
powerful enough to know when somethings monadic result is not used.

        John

-- 
John Meacham - ⑆repetae.net⑆john⑈