| n < # y, perm(x, y[n, a]) ⊦ y = [], a ∈ x ∧ perm(x -1l a, y -1l y[n]) |
n < # y, perm(x, y[n, a]), perm(y[n, a], x) ⊦ y = [], a ∈ x ∧ perm(x -1l a, y -1l y[n])
Used simplifier rules: sym-01: ⊦ perm(x, y) → perm(y, x);%trans: ⊦ perm(x, y) ∧ perm(y, z) → perm(x, z);%ref: ⊦ perm(x, x);