| ⊦ #((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⌝ |
⊦ # σ < ⌜m⌝ + ⌜n⌝ , #((σ from m) to n) = #((σ to m + n) from m) ∧ (⌜n0⌝ < #((σ from m) to n) → ((σ from m) to n)[n0] = ((σ to m + n) from m)[n0])