def seq_at_b
import bendtorch@1.3.0.0/main.bend as Bendtorchimport Base
861def seq_at_b(-P1: Type, -P2: Type, -X: Type, -Y: Type, -Z: Type, -S1: Type, -S2: Type, ba: P1 -> S1 -> Y -> P1 -> Bwd<P1, X>, bb: P2 -> S2 -> Z -> P2 -> Bwd<P2, Y>, p: Two<P1, P2>, s: Two<S1, S2>, dz: Z, g: Two<P1, P2>) -> Bwd<Two<P1, P2>, X>:
862 match p s g:
863 case Two{p1, p2} Two{s1, s2} Two{g1, g2}: seq_at_b2(P1, P2, X, Y, S1, ba, p1, s1, g1, bb(p2, s2, dz, g2))