⊦ ar1 = ar2 ↔ # ar1 = # ar2 ∧ (∀ n. n < # ar1 → ar1[n] = ar2[n])
⊦ ar = [], # ar = #(ar.first + ar.rest) ∧ (∀ n. n < # ar → ar[n] = (ar.first + ar.rest)[n])
Used terms: ar.first + ar.rest, ar