Either andThenK or pipelK seems not quite right

[lrworth]

andThenK : (a -> Return x b) -> (b -> Return x c) -> (a -> Return x c)

which means it needs to be called like

andThenK doFirst doSecond

which is the opposite to andThen.

This is fine, I guess, except that

pipelK = List.foldl andThenK singleton

which means

  pipelK [doFirst, doSecond]

expand pipelK

  List.foldl andThenK singleton [doFirst, doSecond]

expand foldl per https://package.elm-lang.org/packages/elm/core/1.0.5/List#foldl

  singleton
  |> andThenK doFirst
  |> andThenK doSecond

expand |>

  andThenK doSecond (andThenK doFirst singleton)

which has the effect of doing doSecond first, then doFirst. The name pipelK (and the comment "Compose updaters from the left") implies it should be the other way around.

I'd solve this by flipping the type of andThenK, and I am happy to submit a PR, just wanted to check it's the right thing to do.