\ Where tbase is the existing tree structure, and t is the new tree node.
: tree-insert-child { t tbase }
  for 
    t tree->key@ tbase tree->key@ tree-prefix?
    if 
      tbase tree->children@ 0=
      if 
        \ This base has no children yet, so set t as its child.
        t tbase tree->children! exit
      else 
        tbase tree->children@ to tbase 
        tbase t tree-find-relation
        tree-sibling = 
        if
          \ We went deep enough to find a sibling of t.
          tbase t tree-insert-sibling exit
        then
        next
      then
    else
      tbase tree->next@ dup to tbase if next then
    then
  endfor
  abort" no such prefix" ;


  \ NOTE: this frees the input string
: tree-remove { s treevar | tbase prev } 
  treevar tree@ to tbase
  0 to prev
  for
    s tbase tree->key@ tree-prefix?
    if 
      \ We found the right prefix.
      \ Now test if tbase is the exact node we want.
      s tbase tree->key@ string-equal 
      if 
        prev tbase tree-link-prev-to-next
        tbase tree-free
      else 
        \ Check if the first child is the node we want to remove.
        tbase tree->children@ dup tree->key@ s string-equal
        if 
          \ Point tbase's ->children to the ->next of the node we found.
          dup tree->next@ tbase tree->children!
          \ Free the node we found.
          tree-free      
        else 
          \ Go to the next node.
          dup to tbase if next then
        then
      then
    else 
      \ Go to the next node if non-null.
      tbase to prev
      tbase tree->next@ dup to tbase if next then
    then
  endfor
  s string-free ;