Re: avoid the use of default constructors in stl_algo.h

[Doug Gregor <dgregor at cs dot indiana dot edu>]

On Feb 14, 2007, at 3:48 PM, Gunter Winkler wrote:
[snip]
> Thus the open question is: How expensive are default cons, copy cons,
> assign and destruct for "typical" iterators?
>
> I usually have trivial default cons. and trivial destructor, similar
> copy and assignment operations.

Without some kind of measurements that show us what improvements  
we'll see with this change, we can't consider the change on the  
grounds of performance. Performance, especially where compiler  
optimizations are important, is notoriously hard to characterize.

> The second question is: Should the algorithms enforce the existence of
> default constructors - which prohibits some optimizations of later
> assignments - or not?

Default constructors are required for forward iterators, but we're  
not required to use them. I don't think this is an argument for or  
against.

My guess is that you'll need to demonstrate an improvement in  
performance for the libstdc++ maintainers to make this change.

	Cheers,
	Doug