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Proof step 2 from proof lastn-neq-01 (previous step)

lastn(n, x) = b ' + y, a ∈ y, n ≤ # x ⊦ a ∈ x

User applied rule structural induction

And obtained the following new goals

Proof step 3:
lastn(n0 +1, x) = b ' + y, a ∈ y, n0 +1 ≤ # x, ∀ x, b, y, a. lastn(n0, x) = b ' + y ∧ a ∈ y ∧ n0 ≤ # x → a ∈ x ⊦ a ∈ x

Rule argument

indvar: n

Additional information

Used simplifier rules: lastN-zero: ⊦ lastn(0, x) = [];%nat freely generated by 0, +1;;% ⊦ x + y = [] ↔ x = [] ∧ y = []; (as)% ⊦ a ' ≠ []; (s)%a: ⊦ (x + y) + z = x + y + z; from specification list