/*****
* treedef.asy
* Andy Hammerlindl 2003/10/25
*
* Implements a dynamic binary search tree.
*****/

struct tree
{
 tree left;
 tree right;
 int key = 0;
 int value = 0;
}

tree newtree()
{
 return null;
}

tree add(tree t, int key, int value)
{
 if (t == null) {
   tree tt;
   tt.key = key; tt.value = value;
   return tt;
 }
 else if (key == t.key) {
   return t;
 }
 else if (key < t.key) {
   tree tt;
   tt.left = add(t.left, key, value);
   tt.key = t.key;
   tt.value = t.value;
   tt.right = t.right;
   return tt;
 }
 else {
   tree tt;
   tt.left = t.left;
   tt.key = t.key;
   tt.value = t.value;
   tt.right = add(t.right, key, value);
   return tt;
 }
}

bool contains(tree t, int key)
{
 if (t == null)
   return false;
 else if (key == t.key)
   return true;
 else if (key < t.key)
   return contains(t.left, key);
 else
   return contains(t.right, key);
}

int lookup(tree t, int key)
{
 if (t == null)
   return 0;
 else if (key == t.key)
   return t.value;
 else if (key < t.key)
   return lookup(t.left, key);
 else
   return lookup(t.right, key);
}

void write(file out=stdout, tree t)
{
 if (t != null) {
   if(t.left != null) {
     write(out,t.left);
   }
   write(out,t.key);
   write(out,"->");
   write(out,t.value,endl);
   if (t.right != null) {
     write(out,t.right);
   }
 }
}