The function map-processes
calls function on processes.
function is passed each live process (as determined by process-alive-p) in turn as its single argument.
For a process argument p, if function returns nil
then map-processes
continues by calling function on another process, but if function returns true then map-processes
returns p immediately and stops calling function (so function may not get called on all processes).
LispWorks User Guide and Reference Manual - 20 Sep 2017