Discrepancy between mapCLR_ and mapR_.

[yotamDvir]

See example below. For readability, list notation with center denoted by *s is used for a pivot.

mapR_ (List.take 1) [1,2,*3*,4,5] == [1,2,*3*,5]

mapCLR_ identity identity (List.take 1) [1,2,*3*,4,5] == [1,2,*3*,4]

Awkward implementation and lack of testing are to blame.

elm-pivot/Pivot/Map.elm

Lines 70 to 73 in cee1b98

	mapR_ : (List a -> List a) -> Pivot a -> Pivot a
	mapR_ f =
	mapL_ f
	|> mirror

Documentation makes matters worse, as it hints that these two applications above should have the same result.

elm-pivot/Pivot.elm

Lines 530 to 532 in cee1b98

	{-| See `mapCLR_`.
	-}
	mapR_ : (List a -> List a) -> Pivot a -> Pivot a

As for fixing, the following works:

mapR_ = mapCLR_ identity identity

Still, it could be optimized, as mapCLR_ internally reverses the left side twice.