have : ord_sgn (compare n m) ≃ (1:Difference ℕ) := ‹sgn (n——m) ≃ 1›
ℕ : Type
inst✝ : Natural ℕ
n m : ℕ
x✝ : (n——m).sgn ≃ 1
⊢ Positive (n——m)
ℕ : Type
inst✝ : Natural ℕ
n m : ℕ
x✝ : (n——m).sgn ≃ 1
this : ord_sgn (compare n m) ≃ 1
⊢ Positive (n——m)