indique/elm-linear-direction/1.0.2

elm-linear-direction

I think direction can be better expressed than in

• foldr and foldl: does foldr mean fold right? A quite unclear name
• Array.slice's negative indices: slice 0 -1 is handy! But you can't do slice 2 -0
• no getr/l, setr/l, ... but foldr and foldl?

This package's simple goal is allowing you to use types containing the direction

import LinearDirection exposing (LinearDirection(..))
import LinearDirection.Array as Array

Array.fromList [ "e", "l", "m" ]
    |> Array.fold LastToFirst (+) ""
--> "elm"

This has some neat advantages.

• You can deal with both directions at once

  import LinearDirection exposing (LinearDirection(..))
  import LinearDirection.Array as Array
  
  updateAt : Int -> LinearDirection -> (a -> a) -> Array a -> Array a
  updateAt index direction alter =
      Array.replaceAt index direction
          (alter (Array.at index direction))

• this also results in less clutter (e.g. one fold instead of foldr foldl)