Proof step 3 from proof min-add-same (previous step)
⊦ (n0 < n1 ⊃ n + n0;n + n1) = n + (n0 < n1 ⊃ n0;n1)
User applied rule case distinction
And closed the goal!
Rule argument
pos: right 1
Additional information
Used simplifier rules:
⊦ m + n = m + n0 ↔ n = n0; (s)%a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic%c: ⊦ m + n = n + m; from specification nat-basic