⊦ ar1 = ar2 ↔ # ar1 = # ar2 ∧ (∀ n. n < # ar1 → ar1[n] = ar2[n])
m < # ar ⊦ # ar[m, a][m, b] = # ar[m, b] ∧ (∀ n. n < # ar[m, a][m, b] → ar[m, a][m, b][n] = ar[m, b][n])
Used terms: ar[m, b], ar[m, a][m, b]