This library is based on SRFI-111.
Boxes are objects with a single mutable state. Several Schemes have them, sometimes called cells. A constructor, predicate, accessor, and mutator are provided.
Constructor. Returns a newly allocated box initialized to value.
#t if object is a box, and
Accessor. Returns the current value of box.
(set-box! box value)
Mutator. Changes box to hold value.