Did Every Roman Legionary Have a Sling?

Every roman legionary, when he joined up, was taught to swim. He was also taught to use a bow and a sling and the sword and the javelin. And these all put together, his skills were completely across the board when it came to weaponry. The cavalry used a haster, which is a long spear from the saddle. Cavalry also used a longer sword than the legionaries, arthur. One of the things, just by the bye, i find very odd that to our modern minds, a stirrup on a saddle is just so sensible and easy to use. Yet the roman cavalry didn't have stirrups. And i don't know,