) get "input.ivy"

sample = 5 5 rho 3 0 3 7 3 2 5 5 1 2 6 5 3 3 2 3 3 5 4 9 3 5 3 9 0

op visible r =
    r = -1, r
    r = transp max\ transp r
    r = r > -1 flip r
    1 drop r

op vis2 m = (visible m) or (flip visible flip m)
op vis4 m = (vis2 m) or (transp vis2 transp m)

sample
+/, vis4 sample
+/, vis4 input