A number or
A function designator.
wait-reason provides the value returned by process-whostate when called on the current process.
wait-function is called periodically with arguments wait-args . wait-function may be called many times and in several places. Therefore wait-function should be fast and make no assumptions about its dynamic context.
processes all events sent to the current process, including system events such as window messages on Microsoft Windows, and objects sent by other processes via process-send. In the latter case, the objects must be lists of the form
, which cause
to be applied to
(the values are discarded).
LispWorks User Guide and Reference Manual - 21 Dec 2011