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Proof step 4 from proof butlast-length (previous step)

# str = m + 1 ⊦ str = "", # str.butlast = m

User applied rule insert rewrite lemma

And obtained the following new goals

Proof step 5:
⊦ str.butlast = l→s(s→l(str).butlast)
Proof step 6:
# str = m + 1 ⊦ str = "", # l→s(s→l(str).butlast) = m

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 terms: str