items rolled up on both sides of a focus

📜 Scroll

→ good fit for dynamic choice selection: tabs, playlist, ... ↑ examples

Scroll can even focus a gap Down or Up from every item

import Linear exposing (Direction(..))
import Emptiable exposing (filled)
import Stack exposing (topBelow)
import Scroll exposing (Scroll, FocusGap)

Scroll.empty
    --: Scroll item_ FocusGap Possibly
    |> Scroll.focusAlter (\_ -> -1 |> filled)
    --: Scroll number_ FocusGap never_
    |> Scroll.sideAlter Up
        (\_ -> topBelow 1 [ 2, 3 ])
    --: Scroll number_ FocusGap never_
    |> Scroll.toGap Up
    --: Scroll number_ FocusGap Possibly
    |> Scroll.focusAlter (\_ -> 0 |> filled)
    --: Scroll number_ FocusGap never_
    |> Scroll.toStack
--> topBelow -1 [ 0, 1, 2, 3 ]

suggestions?

→ See contributing.md

alternatives

• zwilias/elm-holey-zipper. unsafe; a bit cluttered; no map (Location -> ...), dragFocus, toNonEmptyList, sideAlter (so no squeezing in multiple items, ...)
• turboMaCk/non-empty-list-alias: List.NonEmpty.Zipper complete; cluttered (for example update & map); some unintuitive names
• miyamoen/select-list complete; a bit cluttered; no focusWhere
• yotamDvir/elm-pivot complete; cluttered; no map (Location -> ...)
• staeter/ziplist navigation works; a bit cluttered; no map (Location -> ...), sideAlter (so no squeezing in multiple items, ...)
• wernerdegroot/listzipper navigation works; no dragFocus, map (Location -> ...), toNonEmptyList
• stoeffel/list-focus no clutter included but also no access of before and after, no length, toList, map (Location -> ...), toNonEmptyList
• alexanderkiel/list-selection & NoRedInk/list-selection very incomplete, impossible to extract focused item safely; no navigation, insertion, side, ...
• jjant/elm-comonad-zipper incomplete; no dragFocus, toNonEmptyList, sideAlter (so no squeezing in multiple items, ...)
• guid75/ziplist extremely incomplete
• arowM/elm-reference: Reference.List only overList, sides impossible to access & alter