Proposal: reduce base from the top

[Simon Marlow]

Stefan O'Rear wrote:
> On Tue, Apr 03, 2007 at 02:36:06PM +0100, Ross Paterson wrote:
>> On Tue, Apr 03, 2007 at 11:21:34AM +0100, Simon Marlow wrote:
>>> This is an attempt to propose a set of changes that we could reasonably 
>>> make in the GHC 6.8 timeframe, that would significantly reduce the size of 
>>> base and give us more flexibility to independently develop packages.
>>> [...]
>>> Control.Applicative
>>> Data.Foldable, Data.Traversable
>>> Data.Map, Data.IntMap, Data.Set, Data.IntSet
>>> Data.Sequence, Data.Tree
>>> Data.HashTable
>>> Data.Graph
>>> ---> new package collections? containers?  or split further?
>>>      (dep. on array, generics, concurrent)
>> Data.HashTable (and thus Data.Array.*) is used in the implementation
>> of Data.Typeable.  It also differs from the others in being a mutable
>> data structure.  I imagine that without it this package wouldn't need to
>> depend on array and concurrent.
> 
> I hear that a lot - but as I see it, why does *Typeable* need to be in
> base?  As long as we have a portable Unsafe.Coerce (exists now), and a
> portable equivalent to GHC.Prim.Any (should be trivial to add to both
> Hugs and YHC - names anyone?) Typeable/Dynamic can be a portable
> high-level library. 
> 
> My cursory grepping of the '*.*hs' files in base reveals only one
> non-deriving non-SYB use of Typeable/Dynamic/TypeRep: DynException. 

Separating Typeable and Dynamic from base is certainly something we should try 
to do, but I think this belongs in the next stage.  The DynException dependency 
might be removed if we switch to using extensible exceptions along the lines of 
my Haskell Workshop paper from last year.

Cheers,
	Simon