Packages: exposed, hidden, available (was: Packages and Modules)

[Simon Marlow]

Dimitry Golubovsky wrote:

> I'd suggest the following sub-definition for "available" (other name
> could be "transient"):
> 
> A package which is "available" is not "installed" at (immediately
> known to) a particular developer's system, as opposed to "exposed" and
> "hidden" which are "installed".
> 
> When a package/program is being built that requires a package which is
> not installed, three options are available:
> 
>  - a package is located (on the Internet, using Cabal-get or
> Cabalfind, or manual search), downloaded, and installed (i. e. becomes
> known to the developer's system), and gets into "exposed" or "hidden"
> category
> 
>  - a package is located, downloaded temporarily (i. e. cached) on the
> developer's system*, used for a particular package that requires it
> and discarded afterwards (or lives for some time in the cache).**
> 
>  - package cannot be found (Internet search fails)

This stuff is completely separate, I think.  Automatic downloading and 
installation of packages is handled by the Cabal tools; the compiler is 
not involved, and the present discussion is just about language and 
compiler support.

Cheers,
	Simon