| n0 < # y, ∀ y, a. n0 ≤ # y → a ' + firstn(n0, y) = firstn(n0, a ' + y) + (a ' + y)[n0] ' ⊦ y.first ' + firstn(n0, y.rest) = firstn(n0, y) + y[n0] ', y = [] |
y = a0 + y0, n0 < # y, ∀ y, a. n0 ≤ # y → a ' + firstn(n0, y) = firstn(n0, a ' + y) + (a ' + y)[n0] ' ⊦ a0 ' + firstn(n0, y0) = firstn(n0, y) + y[n0] ', y = []
Used simplifier rules: x ≠ [] ⊦ a = x.first ∧ y = x.rest ↔ x = a + y; (elim) Used terms: y, a0, y0