On 12/06/07, Arend-Jan Wijtzes <ajwytzes@xxxxxxxxxxxx> wrote:
But what puzzles me is that I can actually declare a nameless object like that.
For example the analogy with int would be:
int main()
{
int;
}
which gives the error: "error: declaration does not declare anything".
The analog for int would be int(), which is semantically the same as 0.
Now I'm not advocating that this should be an error for classes, but it would
be nice if there was some mechanism to warn about this. How likely is it that
an author actually intends to create an object and immediately destroy it again
in one line of code, without doing anything with it?
In the simple examples, very unlikely.
However, you can do some fun things thanks to the lifetimes of temporaries:
#include <iostream>
struct output_wrapper {
output_wrapper() { std::cout << "PRELUDE\n"; }
~output_wrapper() { std::cout << "POSTLUDE\n" << std::flush; }
};
int main() {
output_wrapper(), std::cout << "Hello World" << std::endl;
}
Admittedly contrived, but I'm sure you can come up with your own fun
abuses. Maybe use it with scoped_lock to lock for a single statement
without needing to create a block or think up a name the lock object?
~ Scott McMurray
