Re: [boost] Re: container design (Was: std::complex design (Was: N-Dimensional array))

From: Toon Knapen (toon.knapen_at_[hidden])
Date: 2002-03-08 08:31:44

On Friday 08 March 2002 13:46, you wrote:
> ----- Original Message -----
> From: "rwgk" <rwgk_at_[hidden]>
>
> > Without this back door only friend functions could use the
> > mechanism that I just explained. I have no clue how the
> > same effect could be achieved without violating the
> > principle of encapsulation. Personally I have no problem
> > with this pragmatic approach, but as I said, I am not going
> > to argue the case with respect to a standard container.
>
> Here's a thought:
>
> Suppose we could hand vector<T> a chunk of memory and tell it "this
> contains memory for N instances of T, the first M of which have been
> constructed", and have it use that memory?
>
Yesterday I also posted something similar to solve it, in the short term,
with soth like :
double* uninitialised = new double[ ncomplexes * 2 ]
std::vector< complex< double > > v(ncomplexes, uninitialised);

the vector constructor will still need to cast the array to an array of 
complexes (not that this also relies on the discussed layout of a complex)

But once layout and initialisation is covered, what about copying for 
intstance. If I std::copy( complex1_begin, complex1_end, complex2_begin),
is the compiler able to use memcpy (AFAIK it will call the assignment op for 
every one of them)

(hoping this msg will finally make it to the group)