enum data, left, right

function tmap(sequence tree, integer rid)
    tree[data] = call_func(rid,{tree[data]})
    if tree[left]!=null then tree[left] = tmap(tree[left],rid) end if
    if tree[right]!=null then tree[right] = tmap(tree[right],rid) end if
    return tree
end function

function newnode(object v)
    return {v,null,null}
end function

function add10(atom x) return x+10 end function

procedure main()
    object root = newnode(1.00)
    -- Add some nodes.
    root[left] = newnode(1.10)
    root[left][left] = newnode(1.11)
    root[left][right] = newnode(1.12)

    root[right] = newnode(1.20)
    root[right][left] = newnode(1.21)
    root[right][right] = newnode(1.22)

    -- Now the tree has seven nodes.

    -- Show the whole tree.
    ppOpt({pp_Nest,2})
    pp(root)

    -- Modify the whole tree.
    root = tmap(root,routine_id("add10"))

    -- Create a whole new tree.
    object root2 = tmap(root,rid)

    -- Show the whole tree again.
    pp(root)
end procedure
main()