Re: Question on vector at()
On Mar 17, 2:23 am, red floyd <no.s...@here.dude> wrote:
Juha Nieminen wrote:
Jeff Schwab wrote:
I can't think of many applications where at() throwing an exception
would be in any way a desirable thing. (As mentioned, to catch
programming errors IMO using assert() is better.)
Huh? The exception is *exactly* the right solution, for the reasons re=
d
floyd already explained.
Could you please explain to me why is that?
If indexing out of boundaries at some place is an indication of a
programming error, ie. a bug, the best course of action is to report
immediately about this detected error, at the place where it happens.
assert() is exactly the tool designed for this: It terminates the
program immediately, and with the aid of a debugger you can see the
whole stack trace and the values of the variables exactly when the error=
happened. This way the programming error can be fixed, and the indexing
out of boundaries will not happen anymore.
I can't even begin to imagine why throwing an exception instead, and
catching it somewhere else than right where the error happens, would be
a better idea.
Because the correct place to catch the error is not in at(),
or in GetApple(), but rather in the caller of GetApple(), who
will have some sense of what to do with it.
And how will the caller of GetApple() have some sense of what to
do with it? If the argument is the result of a programming
error, and you can't logically isolate the error (and if there
is a programming error, it means that your reasoning about the
program was wrong, so you can't logically say anything about the
program), then there is no place in the code where you can have
some sense of what to do with the error. The only thing to do
is to "propagate" the "exception" somewhere outside of the
corrupted process. Which is really what an assertion failure
does: it is an "exception" which can only be caught and handled
outside the process. (Outside the process, of course, might
even be outside the machine, e.g. a human operator.)
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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