| ⊦ (σ from m) to n = (σ to m + n) from m, # σ < ⌜m⌝ + ⌜n⌝ |
⊦ σ0 = σ1 ↔ # σ0 = # σ1 ∧ (∀ n. ⌜n⌝ < # σ0 → σ0[n] = σ1[n])
⊦ #((σ from m) to n) = #((σ to m + n) from m) ∧ (∀ n0. ⌜n0⌝ < #((σ from m) to n) → ((σ from m) to n)[n0] = ((σ to m + n) from m)[n0]), # σ < ⌜m⌝ + ⌜n⌝
Used terms: (σ to m + n) from m, (σ from m) to n