@[inline]

def List.scanlM {m : Type u_1 → Type u_2} {β : Type u_1} {α : Type u_3} [Monad m] (f : β → α → m β) (init : β) (l : List α) : m (List β)

Folds a monadic function over a list from the left, accumulating partial results starting with init. The accumulated values are combined with the each element of the list in order, using f.

Equations

• List.scanlM f init l = List.reverse <$> List.scanAuxM✝ f init l

@[inline]

def List.scanrM {m : Type u_1 → Type u_2} {α : Type u_3} {β : Type u_1} [Monad m] (f : α → β → m β) (init : β) (xs : List α) : m (List β)

Folds a monadic function over a list from the right, accumulating partial results starting with init. The accumulated values are combined with the each element of the list in order, using f.

Equations

• List.scanrM f init xs = List.scanAuxM✝ (flip f) init xs.reverse

@[inline]

def List.scanl {β : Type u_1} {α : Type u_2} (f : β → α → β) (init : β) (as : List α) : List β

Fold a function f over the list from the left, returning the list of partial results.

scanl (+) 0 [1, 2, 3] = [0, 1, 3, 6]

Equations

• List.scanl f init as = (List.scanlM (fun (x1 : β) (x2 : α) => pure (f x1 x2)) init as).run

@[inline]

def List.scanr {α : Type u_1} {β : Type u_2} (f : α → β → β) (init : β) (as : List α) : List β

Fold a function f over the list from the right, returning the list of partial results.

scanr (+) 0 [1, 2, 3] = [6, 5, 3, 0]

Equations

• List.scanr f init as = (List.scanrM (fun (x1 : α) (x2 : β) => pure (f x1 x2)) init as).run