[GHC] #974: Add unzipEithers, lefts, rights to Data.Either

[Henning Thielemann]

On Wed, 1 Nov 2006 roconnor at theorem.ca wrote:

> I've removed the controvertial isLeft, fromLeft, isRight, fromRight from the
> trac, and added lefts and rights. The controvertial additions can be put in a
> new trac. Let us focus on the the noncontrovertial additions first.
> 
> I've also renamed splitEithers into unzipEithers, which I think is better.

What was the reason against 'partitionEither' ? 'unzip' suggests there is
also a 'zip'.