Bosque

namespace NSMain;

concept Tree provides {
    root: Node;
}

concept Node provides {
    value: Int;
    left: Node?;
    right: Node?;
}

function sum(t: Tree): Int {
    return sum(t.root);
}

function sum(n: Node?): Int {
    if(n == none) {
        return 0;
    }
    else {
        return n.value + sum(n.left) + sum(n.right);
    }
}

entrypoint function main(): Int {
    var t: Tree = Tree@{
        root: Node@{
            value: 5,
            left: Node@{
                value: 3,
                left: none,
                right: none
            },
            right: Node@{
                value: 2,
                left: Node@{
                    value: 8,
                    left: none,
                    right: none
                },
                right: none
            }
        }
    };

    return sum(t);
}