Could be... The only rationale for bit vectors these days, I think, would be when you have to stuff things into hardware registers or send binary codes over serial ports to control devices at something close to the level of a driver. If that's what you're after, then vec() is your friend.

But if you're just trying to save space in memory, don't bother. Use plain integers and letters in a hash or simple array, and you'll get done a lot quicker with fewer mishaps.