MF206: A new trichotomy to set up integers (English)

With marks and anti-marks, the crucial symmetry between natural numbers (Nat) and negative numbers (Neg) becomes much clearer. And we can set up the foundational arithmetic of integers in a logical and solid fashion, based on the fundamental cancellation between a mark and an anti-mark, and the corresponding important role of "nothing". Along with, as usual, the crucial appreciation of the importance of multisets in organizing mathematical objects.

https://www.youtube.com/watch?v=SZmlo49D1NY