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Proof step 5 from proof restn-last (previous step)

n ≤ # x0, ∀ n. n < # x0 → restn(n, x0).last = x0.last ⊦ x0 = [], restn(n, a ' + x0).last = x0.last

User applied rule insert rewrite lemma

And obtained the following new goals

Proof step 6:
⊦ 0 < n → restn(n, x) = restn(n -1, x.rest)
Proof step 7:
0 < n, n ≤ # x0, ∀ n. n < # x0 → restn(n, x0).last = x0.last ⊦ x0 = [], restn(n -1, (a ' + x0).rest).last = x0.last

Rule argument

spec: list-del inst: name: rest-rec seq: ⊦ 0 < n → restn(n, x) = restn(n -1, x.rest) subst: [x, n] → [a ' + x0, n] flags: rewrite, current

Additional information

Used simplifier rules: restN-zero: ⊦ restn(0, x) = x;%zero: ⊦ 0 < m ↔ m ≠ 0; from specification nat-basic1%l-02: ⊦ x ≠ [] → (a ' + x).last = x.last; from specification list-last%a: ⊦ (x + y) + z = x + y + z; from specification list Used terms: a ' + x0, n