Proposal: reduce base from the top

[Donald Bruce Stewart]

simonmarhaskell:
> 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.
> 
> This is not an attempt to solve all the issues we have in one go, but a 
> practical incremental step towards the goal.  I'm not trying to make base 
> compiler-independent for example; that's a worthy goal, but it's not clear 
> (at least to me) how to get there yet.  What I'm doing here is 
> disentangling the dependencies from the top down.  We started on this path 
> before GHC 6.6 (see http://hackage.haskell.org/trac/ghc/ticket/710), this 
> proposal will clarify some the details of the next stage.
> 
> There may be dependencies I've missed, but as far as I'm aware all of the 
> following is possible without any significant rewriting of code.  These 
> reoganisations will allow more reuse: for example, more libraries will be 
> able to make direct use of the unix/Win32 packages rather than being 
> limited to the primitives available in the base package, so cleanups will 
> be possible after the reoganisation.  There are several things I'm not 
> completely sure about, and some naming issues to resolve, so please take a 
> look and comment if you can.
> 
> I'll make one request regarding comments: please don't suggest renaming 
> modules at this point.  There are various modules whose names I'm aware are 
> contentious, but I think it would be a distraction to discuss those as part 
> of this proposal; let's do it separately.
> 
> Here goes:
> 
> System.Time
> --> new package old-time (dep. on unix/Win32)
> 
> System.Locale
> --> new package old-locale
> 
> System.Posix.Signals
> --> unix (System.Cmd depends on it, but moves to new package process)
> 
> System.Directory
> --> new package directory (dep. on filepath, unix/Win32)
>     System.Directory.Internals goes away, use filepath instead
> 
> Data.Array.*
> --> new package array (maybe; I'm slightly dubious here)
>     (dep. on concurrent for Data.Array.Diff)
> 
> Data.Generics.*
> --> generics (maybe; Data class is defined for everything and is derivable)
> 
> Data.ByteString.*
> --> fps (dep. on base, generics, array)

Yep, but we might call it the 'bytestring' package as Ian suggests.
I'm good with this.

> 
> Control.Concurrent.*, System.Timeout
> --> new package concurrent
>     (needed by Data.Unique, where to move it?)
> 
> Control.Parallel.*
> --> new package parallel
> 
> System.Process, System.Cmd
> --> new package process (dep. on concurrent)
> 
> 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)
> 
> System.Console.GetOpt
> ---> new package getopt? consoleutils?
> 
> Text.PrettyPrint.*
> ---> new package pretty
> 
> System.Random
> ---> new package random (modify to use time, not old-time)
> 
> Other modules we could move: Text.Printf, Data.Unique, Data.Monoid, 
> System.CPUTime.
> 
> 
> Topological sort of core packages with dependencies
> ---------------------------------------------------
> base
> unix/Win32       (base)
> generics         (base)
> concurrent       (base)
> parallel         (base)
> filepath         (base)
> Cabal            (base)
> readline         (base)
> regex-base       (base)
> regex-posix      (base, regex-base)
> regex-compat     (base, regex-base, regex-posix)
> parsec           (base)
> stm              (base)
> template-haskell (base)
> pretty           (base) (could drop from core-packages)
> getopt           (base) (could drop from core-packages)
> old-locale       (base)
> old-time         (base, unix/Win32)
> array            (base, generics, concurrent)
> fps              (base, generics, array)
> process          (base, unix/Win32, concurrent)
> directory        (base, unix/Win32, filepath)
> time             (base, unix/Win32)
> random           (base, unix/Win32, time)
> haskell98        (old-time, old-locale, random, directory, process)
> containers       (base, array, generics, concurrent)
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