My votes: On 21.04.14 10:01 PM, João Cristóvão wrote:
Proposal 0: ----------------
Do nothing
-1
Proposal 1: ---------------- Add no new code, but document Data.Either to mention how to use `left` and (+++) from Control.Arrow
-1 That would not show up "first class", e.g. not in synopsis...
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
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
Proposal 5: ----------------
== Proposal 4, using the mapEither name instead.
-1 Unfortunately, that is too close to mapMaybe :: (a -> Maybe b) -> [a] -> [b] which is a misnomer, should have been called filterMaybe.
Proposal 6: ----------------
Implement mapRight in Data.Either
6a) ... as (b -> c) -> Either a b -> Either a c 6b) ... as fmap
+1
Proposal 7: ----------------
Don't implement mapRight, but include documentation in Data.Either stating that it is just fmap.
Where is the radio button?
Proposal 8: ----------------
Bring bifunctors to base.
+1 -- Andreas Abel <>< Du bist der geliebte Mensch. Theoretical Computer Science, University of Munich Oettingenstr. 67, D-80538 Munich, GERMANY andreas.abel@ifi.lmu.de http://www2.tcs.ifi.lmu.de/~abel/