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Proof step 2 from proof sgn-add (previous step)

⊦ sgn(n + m) = 1, m = 0

User applied rule insert rewrite lemma

And obtained the following new goals

Proof step 3:
⊦ n ≠ 0 → sgn(n) = 1

Rule argument

spec: inst: name: sgn-s seq: ⊦ n ≠ 0 → sgn(n) = 1 subst: [n] → [n + m] flags: rewrite, current

Additional information

Used simplifier rules: z-01: ⊦ m + n = 0 ↔ m = 0 ∧ n = 0; from specification nat-basic2%a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic2%c: ⊦ m + n = n + m; from specification nat-basic2 Used terms: n + m