[Haskell] Re: Trying to install binary-0.4
isaacdupree at charter.net
Sun Oct 28 14:25:26 EDT 2007
Thomas Schilling wrote:
> On Sun, 2007-10-28 at 13:49 -0400, Isaac Dupree wrote:
>> Simon Marlow wrote:
>>> Probably it could be made clearer. In 4.2 the idea is that instead of
>>> base-2.0 ==> base-3.0 + directory-1.0 + array-1.0 + ...
>>> you would replace
>>> base-2.0 ==> newbase-1.0 + directory-1.0 + array-1.0 + ...
>>> and additionally have a package base-3.0 that re-exports the whole of
>>> (newbase + directory + array + ...).
>> "Macros" in cabal: Why not just say that depending on base-3.0 actually
>> means that you have to depend on newbase-1.0, and directory-1.0, etc...
>> Why is compiler support needed? is it really possible that I still
>> don't understand?
> You'd still have the problem that every package has to specify this
> "macro" for itself. You'd want some global macro-database to avoid
> this. The better solution would be to just have a package that
> re-exports everything. I.e., the definition of package base-2.0 would
> look something like this:
> if has system has base-3.0, directory, array ...
> exposed-modules: Data.Maybe, Data.List, ...
Of course it would be defined in the same place that base-3.0 would
normally be defined if it existed (hypothetically supposing base was
renamed to newbase in this case). Instead of Haskell code, a cabal file
that just says, in order to depend on this "package", you (meaning the
cabal mechanism, not the users) need to depend on this set of packages
instead - which is repeatedly expanded until only ghc-packages (or the
equivalent for whatever compiler it is) are in the list.
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