def perm_append

bend-mathlib@0.8.1.0 · perm.bend:185

import Base
import bendlib-kernel-list@1.0.0.0/list.bend as K

185# Permuting both operands of an append gives a permutation of the append.
186def perm_append(-A: Data, +xs: List<&2, A>, +xs2: List<&2, A>, +ys: List<&2, A>, -ys2: List<&2, A>, p: K.perm(A, xs, xs2), q: K.perm(A, ys, ys2)) -> K.perm(A, List.append(&2, A, xs, ys), List.append(&2, A, xs2, ys2)):
187  perm_trans(A, List.append(&2, A, xs, ys), List.append(&2, A, ys, xs), List.append(&2, A, xs2, ys2), perm_append_comm(A, xs, ys), perm_trans(A, List.append(&2, A, ys, xs), List.append(&2, A, ys, xs2), List.append(&2, A, xs2, ys2), perm_append_right(A, ys, xs, xs2, p), perm_trans(A, List.append(&2, A, ys, xs2), List.append(&2, A, xs2, ys), List.append(&2, A, xs2, ys2), perm_append_comm(A, ys, xs2), perm_append_right(A, xs2, ys, ys2, q))))