bst_insert(Bst, Key) when Bst == {} -> {Key, null, null};
bst_insert({Root, Left, Right}, Key) when Root > Key ->
  {Root, bst_insert(Left, Key), Right};
bst_insert({Root, Left, Right}, Key) when Root < Key ->
  {Root, Left, bst_insert(Right, Key)};
bst_insert({Root, Left}, Key) -> {Root, Left, Key};
bst_insert(Root, Key) -> {Root, Key, null}.

bst_search(Bst, _) when Bst == {} -> false;
bst_search({Root, _, _}, Key) when Root == Key -> true;
bst_search({Root, Left, _}, Key) when Root > Key ->
  bst_search(Left, Key);
bst_search({Root, _, Right}, Key) when Root < Key ->
  bst_search(Right, Key);
bst_search(Root, Key) ->
  if
    Root == Key -> true;
    Root /= Key -> false
  end.