Cabal and GHC

[Edward Z. Yang]

Excerpts from Simon Peyton-Jones's message of Thu Nov 22 00:32:27 -0800 2012:
> Now, if Cabal can figure out a plan based on an empty database, it can deliver on that plan even in a non-empty database, without messing up any existing installations.

This is an interesting invariant, weaker than the more obvious one:
"Cabal should do the same plan no matter what the state of the database
is" which is in tension with "don't install more than you have to."

Edward