Data update

Task/Visualize-a-tree/XPL0/visualize-a-tree.xpl0

@@ -0,0 +1,36 @@
+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);
+]