shift w (Seq p q) c = seqW (shiftW w p c)
                           (shiftW (w .*. empty p .+. final p) q c)
shift w (Seq p q) c = seqW (shiftW w p c)
                           (shiftW (w .*. empty p .+. final p) q c)
shift w (Seq p q) c = seqW (shiftW w p c)
                           (shiftW (w .*. empty p .+. final p) q c)