purescript-pointed-list

Port of Haskell pointedlist library.

Type

Single type provided by this library is Data.List.Pointed:

newtype Pointed a = Pointed
  { focus ∷ a
  , reversedPrefix ∷ List a
  , suffix ∷ List a
  }

It allows to quickly move focus and update or replace value at the current position.

Operations

Currently this library provides bunch of instances: Foldable, Foldable1, Traversable, Functor, Comonad. If you want to extend this set please don't hesitate to open a PR.

Additionally it implements following operations:

• prev, next, insertLeft, insertRight, deleteLeft, deleteRight, replace, dropPrefix, dropSuffix, atStart, atEnd - O(1)
• first, last - O(n)

Usage example

Pointed list structure can be useful for example when you are implementing history browsing with undo / redo operations.