roc/examples/effect/ConsList.roc

interface ConsList exposes [ConsList, empty, isEmpty, map, len] imports []

ConsList a : [ Cons a (ConsList a), Nil ]

empty : ConsList a
empty = Nil

len : ConsList a -> Int *
len = \list ->
    when list is
        Cons _ rest -> 1 + len rest

        Nil ->
            0


map : ConsList a, (a -> b) -> ConsList b
map = \list, f ->
    when list is
        Cons x xs ->
            Cons (f x) (map xs f)

        Nil ->
            Nil


isEmpty : ConsList a -> Bool
isEmpty = \list ->
    when list is
        Cons _ _ ->
            False

        Nil ->
            True