| perm(x, y[n, a]), n < # y ⊦ a ∈ x ∧ perm(x -1l a, y -1l y[n]), y = [] |
perm(x, y[n, a]), n < # y, 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);