Eof - to return or to throw?

[Dawid Ciężarkiewicz]

I've just asked Kris why mango is not throwing Eof in it's I/O operations
instead of returning it.

After short discusion he told me to ask about your opinons on NG (probably
to stop me from distrupting him ;) ).

So here am I.

Two versions of same functionality.

SomeIOClass {
   /* throws Eof, 0 == nothing available */
   return uint readWithThrowingEof(void[] buf);

   /* -1 == eof, 0 == nothing available */
   return int  readWithReturningEof(void[] buf);
}


Which is better?

I've always thought about returning Eof as an workaround when you can't
throw it or it is too costly. Like in C.

I mean:

try {
   auto amount = io.readWithThrowingEof(buf);
   useData(buf, amount);
} catch (Eof e) {
   /* do smth */
}

Isn't any worse than:

auto amount = io.readWithReturningEof(buf);
if (ammount >= 0) {
   useData(buf, amount);
} else if (ammount == -1) {
   /* do smth */
}

6 lines vs. 6 lines

But when dealing with multiple reads, try block is _much_ better. In ideal
situation you can only have one try {} catch {} and just read, use, read,
use etc. I can come with many examples where catching/throwing Eof is more
flexible both for implementator and library user and the difference is BIG.
Especialy in D with great exception support.

But are there cases where readWithReturningEof is better? Can someone give
me a snippet that we could discuse on? I really have no idea where
returning magical value Eof could be more handy than throwing it.