...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
Get a reference to the lowest layer.
lowest_layer_type & lowest_layer();
This function returns a reference to the lowest layer in a stack of layers.
cannot contain any further layers, it simply returns a reference to itself.
A reference to the lowest layer in the stack of layers. Ownership is not transferred to the caller.