Returns true if and only if obj is a dynamic. No object satisfying
dynamic?satisfies any of the other standard type predicates.
Return the value of the given dynamic in the current dynamic environment.
Change the value of the given dynamic to obj in the current dynamic environment. The returned value is unspecified.
Invoke and return the value of the given thunk in a new, nested dynamic environment in which the given dynamic has been bound to a new location whose initial contents are the value obj. This dynamic environment has precisely the same extent as the invocation of the thunk and is thus captured by continuations created within that invocation and re-established by those continuations when they are invoked.
dynamic-bind macro is not implemented.