Got an exam Wednesday that lumi should study for since it failed that class.

Got an exam Wednesday that lumi should study for since it failed that class. Instead, been learning Koka

// +, 0, - -> 1, 0, -1

fun unfoldr(f : b -> maybe2, init : b) : div list
  match f(init)
    Just2(a, b) -> Cons(a, unfoldr(f, b))
    Nothing2 -> Nil

fun map-if(xs : list, f : a -> a, b : bool) : list
  if b
  then xs.map(f)
  else xs

fun neg-trit(trit : char) : char
  match trit
    '+' -> '-'
    '-' -> '+'
    e -> e

fun bal-tri(x : int) : div list
  unfoldr(fn(n)
    if n != 0
    then match n % 3
      0 -> Just2('0', n / 3)
      1 -> Just2('+', n / 3)
      _ -> Just2('-', n / 3 + 1)
    else Nothing2
  , x.abs).map-if(neg-trit, x.is-neg()).reverse()

-00

+0-+