Returns #t if v is a box, #f otherwise.
Returns a new mutable box that contains v.
Returns a new immutable box that contains v.
Returns the content of box.
Sets the content of box to v.
box : (and/c box? (not/c immutable?) (not/c impersonator?)) old : any/c new : any/c
Atomically updates the contents of box to new, provided that box currently contains a value that is eq? to old, and returns #t in that case. If box does not contain old, then the result is #f.
When Racket is compiled with support for futures, box-cas! uses a hardware compare and set operation. Uses of box-cas! be performed safely in a future (i.e., allowing the future thunk to continue in parallel).