Drastic Prelude changes imminent

[Yitzchak Gale]

First of all, I am very strongly in favor of Lennart's proposal
of slowing down the BBP.

This discussion is now moving in the direction of changes or
alternatives to BBP itself. That is a worthwhile discussion,
but it's not practical until we first come to a conclusion about
Lennart's original proposal. For now, what is on the table is
to find a way to swap BBP, exactly as it is now, in or out
using some simple mechanism like a pragma.

The proposed syntax LANGUAGE Prelude=AlternativePrelude
is nice, but the difficulty in finding a Proposal 3 shows that
this syntax is not good enough. We need a combined
Proposal 1 and Proposal 3 that works something like this:

The base package comes with two versions of each of
the affected modules. Something like this:

Prelude.Traditional
Prelude.Alternative

Data.List.Traditional
Data.List.Alternative

etc.

Then we need some simple mechanism - a LANGUAGE
pragma, or whatever - that swaps all at once which of
the two sets are re-exported by the standard modules.

-Yitz