On the topic of a good name for FPS, I think its fairly widely considered that a packed byte "string" shouldn't be considered a String, and thus FastPackedString is a potentially confusing misnomer. It was always meant as a working title until something replaced Data.PackedString anyway. If this library is to be imported into the base libraries, along with future PackedString.Unicode and so on, layers on top, we should probably get the name right now. I'm disinclined to call it a ByteArray module -- it doesn't really offer array-like operations. And its got nothing much to do with the other Array.* stuff. Instead, how about: Data.ByteString (with a connotation of IntMap) ? That seems to suggest both the stringy-ness of the api, but also the restriction to bytes. -- Don