Haskell 2010: libraries

Heinrich Apfelmus apfelmus at quantentunnel.de
Thu Jul 16 07:31:41 EDT 2009

Simon Marlow wrote:
> Ian Lynagh wrote:
>> Simon Marlow wrote:
>>> But there's a solution: we could remove the "standard" modules from
>>> base, and have them only provided by haskell-std (since base will just
>>> be a re-exporting layer on top of base-internals, this will be easy to
>>> do).  Most packages will then have dependencies that look like
>>>    build-depends: base-4.*, haskell-std-2010
>> We'll probably end up with situations where one dependency of a package
>> needs haskell-std-2010, and another needs haskell-std-2011. I don't know
>> which impls support that at the moment.
> That's the case with base-3/base-4 at the moment.  Is it a problem?

I think the issue raised is the diamond import problem, for instance
that say the list type from  haskell-std-2010  is spuriously different
from the one in  haskell-std-2011 .

This would affect new programs based on the 2011 standard that want to
use older libraries based on the 2010 standard; the point being that the
latter are "intentionally" not updated to the newer standard.

Of course, that's just the base-3 / base-4  issue which can be solved;
it's just that it's not automatic but needs explicit work by
implementors every time there is a new library standard.



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