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Proof step 7 from proof butlast-length (previous step)

# str = m + 1 ⊦ str = "", # s→l(str).butlast = m

User applied rule insert rewrite lemma

And obtained the following new goals

Proof step 8:
⊦ chars ≠ [] → # chars.butlast = # chars - 1

Rule argument

spec: list-last inst: charlist name: lb seq: ⊦ chars ≠ [] → # chars.butlast = # chars - 1 subst: [chars] → [s→l(str)] flags: rewrite

Additional information

Used simplifier rules: ⊦ # s→l(str) = # str;% ⊦ s→l(str) = [] ↔ str = "";% ⊦ n ≤ m → m + n0 - n = (m - n) + n0;% ⊦ n + 0 = n;% ⊦ (m + n0) + n1 = m + n0 + n1;% ⊦ m + n = n + m; Used terms: s→l(str)