folding while mapping?

Stream: Is there code for X?

[Thomas Murrills]

Is there a conventional functional programming name for this function? Does it exist already somewhere?

def foldlMap (f : β → α → (γ × β)) (init : β) (as : Array α) : Array γ × β := Id.run do
  let mut gs := Array.mkEmpty as.size
  let mut b := init
  for a in as do
    let (g,b') := f b a
    b  := b'
    gs := gs.push g
  return (gs, b)

[Kyle Miller]

docs#List.mapAccumr is the list version for foldr

[Kyle Miller]

I know that the Mathematica name for your function is FoldList, though it starts with gs := #[init].

[Thomas Murrills]

I'm looking for the analogue of FoldPairList, haha!

[Thomas Murrills]

(Though actually that's even slightly different as well, since it doesn't return the final accumulated value)

[Thomas Murrills]

Just guessing, but maybe the typical FP strategy here is just to mapM in a state monad, since that's what this is, but it can sometimes be convenient to not have to StateT things...either that or there is no typical strategy, perhaps because for whatever reason people wind up not really having to do this that often.