Proofgold Proof

pf
Let x0 of type ι be given. Let x1 of type ι → ι be given. Apply pack_u_0_eq with pack_u x0 x1, x0, x1. Let x2 of type ι → ι → ο be given. Assume H0: x2 (pack_u x0 x1) (pack_u x0 x1). The subproof is completed by applying H0. ■