| a ∈ y, dups(filter(a ' + x0, y)), ∀ y0. ¬ dups(filter(x0, y0)) ⊦ a ∈ x0, dups(x0) |
a ∈ y, dups(filter(x0, y)), ∀ y0. ¬ dups(filter(x0, y0)) ⊦ a ∈ x0, dups(x0)
Used simplifier rules: filt-y: ⊦ a ∈ y → filter(a ' + x, y) = a ' + filter(x, y);%in-01-01: ⊦ a ∈ y → (a ∈ filter(x, y) ↔ a ∈ x);%rec: ⊦ dups(a ' + x) ↔ ¬ ¬(a ∈ x ∨ dups(x)); from specification list-dup%a: ⊦ (x + y) + z = x + y + z; from specification list