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Proof step 2 from proof butlast-in (previous step)

char ∈ str.butlast ⊦ str = "", char ∈ str

User applied rule insert rewrite lemma

And obtained the following new goals

Rule argument

spec: string-ops inst: name: butlast-def seq: ⊦ str.butlast = l→s(s→l(str).butlast) subst: [str] → [str] flags: rewrite, current

Additional information

Used simplifier rules: char-in: ⊦ char ∈ l→s(chars) ↔ char ∈ chars;%char-in-01: ⊦ char ∈ s→l(str) ↔ char ∈ str;% ⊦ s→l(str) = [] ↔ str = "";%chars ≠ [] ⊦ char ∈ chars.butlast → char ∈ chars; (forward) Used terms: str