| ⊦ perm(x, a ') ↔ x = a ' |
Used simplifier rules: perm-r: ⊦ y ≠ [] → ¬ perm([], y);%del-01: ⊦ perm(a ' + x, y) ↔ ¬ ¬(a ∈ y ∧ perm(x, y -1l a));%empty: ⊦ perm(x, []) ↔ x = [];%ref: ⊦ perm(x, x);%list freely generated by [], +;;%c: ⊦ a + x = a ' + x; from specification list%in-17: ⊦ a ∈ b ' ↔ a = b; from specification list%one-01: ⊦ a ' -1l a = []; from specification list-del%a: ⊦ (x + y) + z = x + y + z; from specification list%app: ⊦ x + [] = x; from specification list%c-04: ⊦ a ' = b ' ↔ a = b; from specification list%c-03: ⊦ a ' = b ' + x ↔ a = b ∧ x = []; from specification list%e: ⊦ a ' ≠ []; from specification list