Defines a parametric tree:
type 'a tree = Leaf of 'a | Node of 'a tree list
let rec flatten t =
match t with
| Leaf x -> [x]
| Node ts -> List.concat (List.map flatten ts)
Test tree has 3 levels of nesting:
Node [Leaf 1; Node [Leaf 2; Leaf 3];
Node [Node [Leaf 4]; Leaf 5; Leaf 6];
Leaf 7]
flattens to [1;2;3;4;5;6;7] -> sum = 28.
Tests parametric ADT, mutual recursion via map+self, List.concat.
55 baseline programs total.
