error checking

[utzoo!watmath!jcwinterton]

	Somewhat like Bill Paulson, I don't think the idea of PL/1 type ON
units are a particularly good idea.  However, it does provide neat error
trapping if handled correctly and a reasonable repair and return or
give up and quit neatly mechanism is available.  As for that unsettled feeling,
how would one handle a piece of hardware that operates in this way?  At least
one cpu I know of does exactly, by hardware, what the ON unit idea does.
That is, on the interrupt or fault it lays down a new stack frame and transfers
to the appropriate handler through a linkage vector.  Much hardware does this,
in fact, so that some similar mechanism should really exist in a language that
purports to be for system programming (operating system that is) purposes.
Sigh.  It appears that one is d..ned if one does and d..ned if one doesn't.

John Winterton.