ifclass StringTree1
static void addToStringTree(StringTree1 tree, L<S> tok) {
  if (empty(tok)) { tree.leaf = true; ret; }
  S s = first(tok);
  StringTree1 t = tree.getOrAdd(s);
  addToStringTree(t, dropFirst(tok));
}
endif

ifclass StringTree2
static <A> void addToStringTree(StringTree2<A> tree, L<S> tok, A leafValue) {
  if (empty(tok)) { tree.leafValue = leafValue; ret; }
  S s = first(tok);
  StringTree2 t = tree.getOrAdd(s);
  addToStringTree(t, dropFirst(tok));
}
endif