Traversable
Definitions
def for(t: t[a], f: a -> m[b] \ ef): m[t[b]] \ efSourceReturns the result of applying the applicative mapping function f to all the elements of the
data structure t.
for is traverse with it's arguments flipped.
def mapAccumLeft(f: acc -> (a -> (acc, b) \ ef), start: acc, t: t[a]): (acc, t[b]) \ efSourceReturns the result of applying f to the traversable structure t and the initial state acc.
The result is a pair of the final state and the updated copy of the structure.
mapAccumLeft is essentially the combination of map and foldLeft - like map it returns an updated copy
of the initial structure, like foldLeft it passes an updating accumulator through each step of the traversal.