English
If a.out = b.out for erased elements a,b then a = b; (extensionality principle for erased).
Русский
Если a.out = b.out для стертых элементов a,b, то a = b; принцип экстенсиональности для стертых.
LaTeX
$$$\\forall a,b:\\mathrm{Erased}\\,\\alpha,\\ a.\\mathrm{out} = b.\\mathrm{out} \\Rightarrow a = b$$$
Lean4
@[nolint docBlame]
unsafe def nextDnPos (e m) (v : ValidFinite e m) : Float :=
match h : m with
| 0 => nextUpPos _ _ Float.Zero.valid
| Nat.succ m' =>
if ss : m'.size = m.size then Float.finite false e m' (by subst h; unfold ValidFinite at *; rw [ss]; exact v)
else if h : e = emin then Float.finite false emin m' lcProof else Float.finite false e.pred (2 * m' + 1) lcProof
