Re: Ada and Automotive Industry

[stt@houdini.camb.inmet.com (Tucker Taft)]

Robert Dewar (dewar@merv.cs.nyu.edu) wrote:
: T.E.D. says

: "Hmmm. Can I take this to mean that it is not a good idea to raise
: predefined exceptions manually? Are predefined exceptions somehow
: handled differently than user-defined ones?"


: Yes, see RM 11.6

Hmmm...  Language-defined *checks* (which can raise predefined exceptions)
are handled specially.  In particularly, they need not raise an exception
at all if the otherwise "undefined" result would not be used by the
rest of the computation, and if they are raised due to the failure
of such a check, the "location" of the raise need not be precisely
determinable.

However, when an exception is raised explicitly, it makes no
difference whether it is predefined or user-defined -- the
rules are identical.  

Of course, once you get to a handler for a predefined exception, you don't
know as much since it might be due to a failure of a language
defined check (and hence might be imprecise), or it might be due to 
an explicit "raise" (in which case it is fully "precise").

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA