English
Prepending the head of a vector to its tail yields the original vector.
Русский
Префиксация головы вектора к его хвосту восстанавливает исходный вектор.
LaTeX
$$$\\mathrm{cons\\_head\\_tail} : \\forall v : \\text{Vector } α (\\text{succ } n), \\mathrm{cons}(\\mathrm{head}\,v, \\mathrm{tail}\,v) = v$$$
Lean4
/-- Prepending the head of a vector to its tail gives the vector. -/
@[simp]
theorem cons_head_tail : ∀ v : Vector α (succ n), cons (head v) (tail v) = v
| ⟨[], h⟩ => by contradiction
| ⟨_ :: _, _⟩ => rfl