Haskell Platform Proposal: add transformers and revise the mtl package to depend on it

[Duncan Coutts]

On 16 September 2010 12:43, Felipe Lessa <felipe.lessa at gmail.com> wrote:
> On Thu, Sep 16, 2010 at 5:23 AM, Ross Paterson <ross at soi.city.ac.uk> wrote:
>> If this proposal is accepted, monads-fd would be obsoleted and
>> transformers would be turned over to community control (like the current
>> mtl package).
>
> So, if this proposal is accepted, then we would have:
>
> - transformers on HP.
> - mtl on HP (depending on transformers).
> - monads-tf on Hackage (depending on transformers).
>
> Wouldn't it be better to obsolete mtl and have:
>
> - transformers on HP.
> - monads-fd on HP (depending on transformers).
> - monads-tf on Hackage (depending on transformers).
>
> The naming would be more consistent.

It's true that the naming scheme would be more consistent, however I
think the more important point is to communicate clearly to users of
the platform what it is that they need to do.

Consider some Haskell programmer who is not reading this mailing list.
They use the platform and mtl-1 in their code. If the next HP release
contains mtl-2 then it is clear to them what they need to do: they
just need to test their code against mtl-2 (fixing any compilation
problems and adjusting build-depends version constraints). If on the
other hand we removed mtl-1 from the platform then our example coder
does not know what to do. It's much more work for them to discover
that this new package monads-fd was just added to the platform and it
seems to provide the same modules.

Duncan