⊦ ar0 + ar1 = copy(ar1, 0, resize(ar0, # ar0 + # ar1), # ar0, # ar1)
n < # ar1 ⊦ copy(ar1, 0, resize(ar0, # ar0 + # ar1), # ar0, # ar1)[# ar0 + n] = ar1[n]
Used terms: ar1, ar0