| a ∈ y, ∀ a, y. a ∈ y → (a ∈ filter(x0, y) ↔ a ∈ x0) ⊦ a0 ∈ y, a ∈ filter(a0 ' + x0, y) ↔ a = a0 ∨ a ∈ x0 |
a ∈ y, ∀ a, y. a ∈ y → (a ∈ filter(x0, y) ↔ a ∈ x0) ⊦ a ∈ filter(x0, y) ↔ a ∈ x0, a0 ∈ y
Used simplifier rules: filt-n: ⊦ ¬ a ∈ y → filter(a ' + x, y) = filter(x, y);%a: ⊦ (x + y) + z = x + y + z; from specification list