This notion is introduced in a pedagogical way here http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2013/n3580.pdf http://www.open-std.org/JTC1/SC22/WG21/doc

This notion is introduced in a pedagogical way here http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2013/n3580.pdf http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2013/n358...