Re: I keep running into long term c++ programmers who refuse to use exceptions
In article
<ebd4c02a-99cc-41c1-8f80-c6baa8a35f1a@o3g2000yqb.googlegroups.com>,
"WalterHoward@gmail.com" <walterhoward@gmail.com> wrote:
Bad Use: Don't "half-use" exceptions
Many programmers, and even the standard library, have the idea that
exceptions should be reserved for "fatal" errors only. They still use
old style return codes in many functions. There is a huge flaw in the
logic of this approach.
I'm one of those many programmers, and I see a huge flaw in only using
exceptions (as well as a huge flaw in only using return codes, such as
espoused at <http://www.joelonsoftware.com/items/2003/10/13.html>).
The analogy I like to give is that using return codes is like driving on
surface streets, while using exceptions is like taking the expressway.
Each has an appropriate use.
A failure to perform its function is fatal to
the function involved.
You are assuming a function even knows that it failed. Functions
usually have no idea why they are being called.
Take std::find. Is it really "failure" if it returns its second
parameter? Doesn't it really depend on whether or not the caller
expects the element to be in the range being searched? What if the
caller looked like:
// Bug if element is still in c
assert(std::find(c.begin(), c.end(), element) == c.end());
If std::find, instead of returning c.end() to indicate the element isn't
in the range, threw find_exception, the code would be a bit messier, as
in:
#ifndef NDEBUG
// Bug if element is still in c
try { std::find(c.begin(), c.end(), element); assert(false); }
catch (find_exception&) {}
#endif
The inversion of having failure detection inside a try block and having
success be the empty catch block makes this code much harder to
understand, yet there really is no way around it if you are using
exceptions instead of return codes, because the callee, not the caller,
has to decide what is "success" and what is "failure".
Things that are expected to be handled directly by the caller are
usually sent in return codes; things that are expected to be handled at
a much higher level are usually sent via exceptions (at least in the
code that I have influence over).
--
Nevin ":-)" Liber <mailto:nevin@eviloverlord.com> 773 961-1620
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