moving Foldable and Traversable to Prelude (Re: Control.Monad proposal: Add whenJust)

Henning Thielemann lemming at
Wed May 15 22:51:34 CEST 2013

On Wed, 15 May 2013, Edward Kmett wrote:

> Personally, I'd be all for just moving Foldable (and Traversable) into the Prelude and retiring the
> monomorphic versions of the functions they supply. Both abstractions have born the test of time, and its
> hard to even envision Haskell without them at this point.
> I'm somewhat leery that we coud get this proposal past the "but it makes it harder to introduce people to
> Haskell" backlash, but I'd wholeheartedly support it.


1. Prelude should be backwards compatible and since it is implicitly 
imported everywhere, barriers for changing something should be especially 

2. I see a shift away from Prelude functions to more generalized functions 
(Foldable.mapM_, Traversable.mapM, Category.(.), RMonad, alternative 
numeric classes etc.) This way people have to import identifiers 
explicitly, which is a good idea anyway.

More information about the Libraries mailing list