Symbols (variants with our without parameters) and integers are unboxed, while floats are not (but in a few specific cases such as arrays of floats, and iiuc th

Symbols (variants with our without parameters) and integers are unboxed, while floats are not (but in a few specific cases such as arrays of floats, and iiuc that's an inelegant special case on its way out, as it prevents other optimisations).