| dups((a ' + x0) \ y), ∀ y0. ¬ dups(x0 \ y0) ⊦ dups(x0), a ∈ x0, a ∈ y |
dups(x0 \ y), ∀ y0. ¬ dups(x0 \ y0) ⊦ dups(x0), a ∈ y, a ∈ x0
Used simplifier rules: diff-n: ⊦ ¬ a ∈ y → (a ' + x) \ y = a + (x \ y);%diff-in: ⊦ a ∈ x \ y ↔ a ∈ x ∧ ¬ a ∈ y;% ⊦ dups(a ' + x) ↔ a ∈ x ∨ dups(x); (s)%a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ a + x = a ' + x; (s)