🚀 go-pugleaf

bradlee@cg-atla.UUCP (Rob Bradlee) writes:
>/utility_procedure {
>	mark
...stuff...
>	{
>	% test was true.  Process the rest of the items on the stack.
>	}
>	{
>	% test failed. cleanup.
>	cleartomark
>	}  ifelse
>} def

>Is the cleartomark a legitimate way to make sure you've left the stack in good
>shape or a cheap trick that absolves you from the effort of thinking?

Glenn Reid took the "cheap trick" position, which I think is true most of
the time.  However, if testing and processing arguments, managing inter-
mediate results, etc., gets complex enough, I think the mark...cleartomark
is cleaner and clearer than a proc which ends something like:
		} {
			pop pop
		} ifelse
		pop
	} {
		exch pop pop
	} ifelse
...as you try to dig your way back and balance the stack at the end.  This
is hardest in a proc which is coping with error situations and trying to
invoke error handlers with the right stack context.
-- 
Dick Dunn    rcd@raven.eklektix.com   -or-   raven!rcd    Boulder, Colorado
				Cats!