| ⊦ x.butlast + a ' = x ↔ a = x.last, x = [] |
x.butlast + a ' = x, a ∈ x ⊦ a = x.last, x = []
Used simplifier rules: butlast-last: x ≠ [] ⊦ x.butlast + x.last ' = x;%in-15: ⊦ x + a ' = y → a ∈ y; (forward) from specification list%a: ⊦ (x + y) + z = x + y + z; from specification list