Error Signalling

[David C. Plummer <DCP@QUABBIN.SCRC.Symbolics.COM>]

    Date: Fri, 27 Jun 1986  20:04 EDT
    From: "Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>


	I think changing "is an error" in all cases to "signals an error" would
	violate the /Portability/ motivation on page 1 of the Silver Bible.

	I think we (or the standards committee) have to carefully at all the "is
	an error" and decide if it should be "signals an error".  Many of us
	agree number of argument checking should be signalled unless safety is
	completely turned off, and that even then implementations are encouraged
	to check.

    Please, let's not go running off on a tangent.  I was not suggesting
    that EVERY case of "is an error" be changed to "signals an error".  I
    was merely asking whether people thought that cases like the ones I
    enumerated (arg count checking, arg type checking for certain built-in
    functions, and array bounds checking) should be tightened up.  
Sorry.  Yes for all three of those, unless safety is turned completely
off, and even then implementations are encouraged to be safe if
possible.
    After
    we've decided how to handle these cases in general we can start
    discussing which errors are so hard to check that they should be exempt
    from the signalling requirement.

    -- Scott