Fredrik Eriksson wrote:
> On Tue, 02 Sep 2008 22:22:46 +0200, Darren New <dne### [at] sanrrcom> wrote:
>> One of my problems with learning C++ is the number of places where, 
>> instead of saying "This is what this feature does", people say "this 
>> is how you use this feature."
> 
> Perhaps because the rules are sometimes so complex that few really know 
> exactly what a particular feature does under all conditions. It is much 
> easier to say "if you do it like this, it works" than to list all the 
> many cases where it does something slightly or vastly different.

Yeah, basically.  "We don't actually know what the semantics are. We 
just all know the idioms for using the feature."

>> What is a "move constructor"? When would you be "moving" some value?
> 
> "Moving" a value is useful when you know that the source value will be 
> discarded anyway right after the copy is performed, e.g. if it is the 
> return value of a function. Many objects that are expensive to copy can 
> be "moved" much more efficiently.

But the rvalue thing doesn't move a value. What does the rvalue thing 
actually *do* that's different from anything else?  Isn't it that it 
points to a temporary with a guarantee of no aliases?

> Note that non-temporaries can also be bound to r-value references, but 
> not implicitly.

Well, yes, because C++ lets you break anything. That's not the point, 
tho. :-)

-- 
Darren New / San Diego, CA, USA (PST)

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