int  SDown, SLast, SNone;

proc Tree(Root, Head);
int  Root, Head;
int  Col(2), Tail, R;
def \Stem\ Str, Next;
[Col(Str):= 0;  Col(Next):= 0;
Tail:= Head;
loop    [if Tail = 0 then quit;
        Text(0, Tail(Str));
        if Tail(Next) = 0 then quit;
        Tail:= Tail(Next);
        ];
Text(0, "--");  IntOut(0, Root);  CrLf(0);

if Root <= 1 then return;

if Tail # 0 then
    if Tail(Str) = SLast then
        Tail(Str):= SNone;

if Tail = 0 then [Tail:= Col;  Head:= Col]
            else  Tail(Next):= Col;

while Root do   \\ make a tree by doing something random
    [R:= 1 + Ran(Root);
    Root:= Root - R;
    Col(Str):= if Root # 0 then SDown else SLast;
    Tree(R, Head);
    ];
Tail(Next):= 0;
];

[SDown:= "  |";  SLast:= "  `";  SNone:= "   ";
Tree(8, 0);
]