English
There is a dual construction embedding from down ℕ to up ℤ sending n to p−n, dual to the previous one, preserving the relation structure via an IsRelIff instance.
Русский
Существуют дважды взаимно противоположных вложения: из down ℕ в up ℤ с отображением n ↦ p−n, сохраняющее отношение через IsRelIff.
LaTeX
$$$\\text{embeddingUpIntLE}(p):\\mathrm{Embedding}(\\mathrm{down}\\mathbb{N})(\\mathrm{up}\\mathbb{Z})$,\\; f(n)=p-n$$$
Lean4
/-- The embedding from `down ℕ` to `up ℤ` which sends `n : ℕ` to `p - n`. -/
@[simps!]
def embeddingUpIntLE : Embedding (down ℕ) (up ℤ) :=
Embedding.mk' _ _ (fun n => p - n) (fun _ _ h => by dsimp at h; cutsat) (by dsimp; cutsat)