accumulate

Accumulate provides the Fold, Reduce, and Split abstractions.

1. Fold * Use an input to accumulate over some state * Examples: List.foldl, Dict.foldl
2. Reduce * A Fold where the input and state share the same type * Examples: sum, ++
3. Split * Extract an item from a collection, if it exists * Examples: String.uncons, head :: tail * This is mostly useful in the context of reducing over a collection

extension

Fold, Reduce, and Split are already defined for built-in types, but you can easily extend them to your types with the custom function.

examples

Cons to a list if the element exists:

maybeCons =
  Fold.maybe Fold.list

Fold.merge maybeCons [ 2, 3, 4 ] (Just 1)
-- [ 1, 2, 3, 4 ]

Get the minimum value of a list:

minimum =
  Reduce.listLeft (Reduce.min Sort.int)

minimum [ 8, 5, 7 ]
-- Just 5