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Proof step 11 from proof fix-butlast (previous step)

n < # bytes ⊦ bytes = [], # bytes = 1, n = 0, lastn(n, bytes.butlast) = lastn(n + 1, bytes).butlast

User applied rule insert rewrite lemma

And obtained the following new goals

Proof step 12:
⊦ n ≠ 0 → lastn(n, bytes) = lastn(n -1, bytes.butlast) + bytes.last

Rule argument

seq: ⊦ n ≠ 0 → lastn(n, bytes) = lastn(n -1, bytes.butlast) + bytes.last subst: [bytes, n] → [bytes, n + 1] rotate: F spec: list-del inst: bytelist name: lastn-rec

Additional information

Used simplifier rules: ⊦ (m + 1)-1 = m;% ⊦ (m + n0) + n1 = m + n0 + n1;% ⊦ m + n = n + m;% ⊦ bytes + by = bytes + by ';% ⊦ (bytes + by ').butlast = bytes;% ⊦ (bytes + bytes0) + bytes1 = bytes + bytes0 + bytes1;% ⊦ m + 1 ≠ 0; Used terms: bytes, n + 1