Libraries Digest, Vol 128, Issue 72

[Benno Fünfstück]

>
> On 2014-04-21 at 22:01:34 +0200, Jo?o Crist?v?o wrote:
> > Proposal 1:
> > ----------------
> > Add no new code, but document Data.Either to mention how to use `left`
> and
> > (+++) from Control.Arrow
>

+1, I'd also like if Data.Either reexported those functions. Then, the
documentation could just give some
more specific type signatures that show how to use them (like the lens
library does in many cases).


> > Proposal 2:
> > ----------------
> > Document Control.Arrow to exemplify the (->) instance usage.
>

+1

> Proposal 3:
> > ----------------
> >
> > Implement mapLeft in Data.Either
> >
> > 3a) ... as (a -> b) -> Either a c -> Either b c (so that is easy to
> follow)
> > 3b) ... as Control.Arrow.left
> > 3c) ... and also redefine the -> instance of Control.Arrow.left as
> mapLeft
>
>
-1, just export left from Data.Either and give it a more specific type
signature in the documentation.


>
> > Proposal 4:
> > ----------------
> >
> > Implement mapBoth in Data.Either
> >
> > 4a) ... as (a -> b) -> (c -> d) -> Either a c -> Either b d (so that is
> > easy to follow)
> > 4b) ... as Control.Arrow.(+++)
> > 4c) ... and also redefine the -> instance of Control.Arrow.(+++) as
> mapBoth
>
>
-1, same reason as 3  (using +++)


> > Proposal 5:
> > ----------------
> >
> > == Proposal 4, using the mapEither name instead.
>
>
-1


>
> > Proposal 6:
> > ----------------
> >
> > Implement mapRight in Data.Either
> >
> > 6a) ... as (b -> c) -> Either a b -> Either a c
> > 6b) ... as fmap
>
>
-1, fmap is already in Prelude and well-known


>
> > Proposal 7:
> > ----------------
> >
> > Don't implement mapRight, but include documentation in Data.Either
> stating
> > that it is just fmap.
>
>
+1


>
> > Proposal 8:
> > ----------------
> >
> > Bring bifunctors to base.
>

+1
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