Re: Unusual C construct - What is it?

From:
=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 25 Dec 2007 18:40:39 GMT
Message-ID:
<H8ccj.2032$R_4.1478@newsb.telia.net>
On 2007-12-25 18:47, mczard@poczta.onet.pl wrote:

const struct ast_datastore_info dialed_interface_info = {
        .type ="dialed-interface",
        .destroy = dialed_interface_destroy,
        .duplicate = dialed_interface_duplicate,


This is part of C99 syntax and those variables are designated
initialisers. It makes it easier to track which fields are set during
that initialization. It is not valid in C++ though.


If you need such a thing in C++, you have to use external
configuration files (try http://harpoon.sourceforge.net; my project to
be honest). I really wish it were a part of C++, as well as list
literals; and not only for initialization. For example:


The fact that C++ have constructors mitigates the problem slightly, and
if that is not enough you can use comments.

struct Point {
  Point(intx, int y);
};

Point(/*x = */ 10, /*y = */ 25);

draw_line( Point( x = 10, y = 25 ), Point( x = 50, y = 25 ) );

std::vector<int> list( { 1, 4, 5, 2 } );


Will be in the next version of the standard, but with slightly different
syntax.

--
Erik Wikstr?m

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