list reduce

Stream: new members

[Daan van Gent]

I am looking for a function on lists that does the following:

def list.reduce {α β : Type*} (f : β → α → α) : list β → α → list α
| [] a := [a]
| (b :: l) a := a :: list.reduce l (f b a)

example {α : Type*} (l : list (set α)) : list (set α) :=
list.reduce (λ s t, s ∪ t) l ∅

It should produce from the list [s,t,u] the list [∅,s,s ∪ t,s ∪ t ∪ u]. I feel like it should be in mathlib, but it is apparently not called what I would expect it to.

[Mauricio Collares]

Let's try docs#scanl

[Mauricio Collares]

docs#list.scanl seems to exist