Method erase

src/include/cpp-btree/btree.h:1998–2031

template <typename P>
auto btree<P>::erase(iterator iter) -> iterator {
  bool internal_delete = false;
  if (!iter.node->leaf()) {
    // Deletion of a value on an internal node. First, move the largest value
    // from our left child here, then delete that position (in remove_value()
    // below). We can get to the largest value from our left child by
    // decrementing iter.
    iterator internal_iter(iter);
    --iter;
    assert(iter.node->leaf());
    params_type::move(mutable_allocator(), iter.node->slot(iter.position),
                      internal_iter.node->slot(internal_iter.position));
    internal_delete = true;
  }

  // Delete the key from the leaf.
  iter.node->remove_value(iter.position, mutable_allocator());
  --size_;

  // We want to return the next value after the one we just erased. If we
  // erased from an internal node (internal_delete == true), then the next
  // value is ++(++iter). If we erased from a leaf node (internal_delete ==
  // false) then the next value is ++iter. Note that ++iter may point to an
  // internal node and the value in the internal node may move to a leaf node
  // (iter.node) when rebalancing is performed at the leaf level.

  iterator res = rebalance_after_delete(iter);

  // If we erased from an internal node, advance the iterator.
  if (internal_delete) {
    ++res;
  }
  return res;
}

template <typename P>
auto btree<P>::rebalance_after_delete(iterator iter) -> iterator {