∀[L:Top List]. ((colength(L) = 0 ∈ ℤ)
(L ~ []))
{ (Auto THEN (Unfold `list` 1 THEN D 1) THEN colistD 1 THEN Unfold `nil` 0 THEN Auto) }
1. u : Top
2. v : colist(Top)
3. [%2] : (colength([u / v]))↓
4. colength([u / v]) = 0 ∈ ℤ
⊢ [u / v] ~ ⋅