mem (11/02/82)
c I'd like to dispute the notion that the "on event" construct is improper. Thank you, thank you. The opinion seems to be that exception handlers are unclean, because they lead away from a clear flow of control. They do. When you have an operating system to take care of all the assorted spontaneous happenings in and around your computer, the need for local service routines seems to be partially obviated. Partially. But what is going on around you? Do you use co-routines? and think of them as clean? Do you wait for the completion of every operating system function, or do you use a proceed option. For every proceed call you issue, you're explictly declaring the knowledge of background work (i.e., exception-level) being done. For that matter, many operating system calls make this declaration. And once you start writing code which isn't destined to have that operating system support, exception handling is pretty much mandated. Look also at typical real-time multitasking systems, wherein tasks are generally servers for particular functions, on demand. It is handy to be able to express this demand as an asynchronous trap, and it would be nice to have support for this in the implentation language. Mark Mallett