English
If fundamentalSequence o = Sum.inl none, then fastGrowing o equals the successor function.
Русский
Если фундаментальная последовательность o равна Sum.inl none, то fastGrowing o равняется функции следующего.
LaTeX
$$$\\text{fastGrowing\\ o} = \\operatorname{succ}$$$
Lean4
theorem fastGrowing_def {o : ONote} {x} (e : fundamentalSequence o = x) :
fastGrowing o =
match (motive := (x : Option ONote ⊕ (ℕ → ONote)) → FundamentalSequenceProp o x → ℕ → ℕ) x,
e ▸ fundamentalSequence_has_prop o with
| Sum.inl none, _ => Nat.succ
| Sum.inl (some a), _ => fun i => (fastGrowing a)^[i] i
| Sum.inr f, _ => fun i => fastGrowing (f i) i :=
by
subst x
rw [fastGrowing]