Burning bridges

[Edward Kmett]

This discussion currently is limited in scope to the types and combinators
from Foldable and Traversable.

As a concrete proposal, I proposed replacing the combinators in the Prelude
that are duplicated from Foldable and Traversable, with the possible
exception of 'concat' and 'concatMap'.

Any further generalization would be a separate proposal.

-Edward


On Wed, May 22, 2013 at 11:16 AM, Ben Gamari <bgamari.foss at gmail.com> wrote:

> I'm another from the crowd of silence observers. It seems to me that
> we still don't have a fully specified proposal. In particular which
> functions are we discussing? Only those from Traversable and Foldable?
> map? It would be nice to make this clear with a concrete proposal.
>
> Despite this, here's my 2-pence,
>
> +1  Generalise Prelude.mapM etc
>  0  Remove Prelude.mapM etc
> -1  Add more monomorphic variants to Prelude (e.g. whenJust)
> -1  Nothing
>
> The monomorphic elements of the Prelude are an aesthetic wart and a
> significant inconvenience. Being a beginner in the not so distant past,
> I am also skeptical that these functions are significantly easier for
> beginners to grasp and use.
>
> Concerning removing mapM without replacement: I'd be concerned that
> moving such a frequently used function out of the Prelude might be a bit
> confusing for beginners. Given the prominence of Monads in Haskell,
> it might be perplexing to find (f)map exported by the Prelude yet not
> mapM.
>
> On the note of the mtl's exports, Wren suggests that removing this has
> been discussed previously to no avail. My Google-fu might be failing me
> but all I've been able to find is this[1] lone message. At the risk of
> introducing yet another code-breaking change, is there a reason removing
> these re-exports hasn't been discussed further?
>
> Cheers,
>
> - Ben
>
>
> [1] http://www.haskell.org/pipermail/libraries/2005-December/004666.html
>
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