D vs C++

[Andrei Alexandrescu]

On 12/27/10 10:01 AM, Caligo wrote:
> On Mon, Dec 27, 2010 at 7:20 AM, Jonathan M Davis <jmdavisProg at gmx.com
> <mailto:jmdavisProg at gmx.com>> wrote:
>
>     On Monday 27 December 2010 04:41:37 spir wrote:
>      > On Sun, 26 Dec 2010 12:06:04 -0800
>      >
>      > Walter Bright <newshound2 at digitalmars.com
>     <mailto:newshound2 at digitalmars.com>> wrote:
>      > > 11. generative programming
>      >
>      > Does someone have a pointer to any kind of doc about this? (in D)
>
>     Anything on templates, template mixins, and string mixins. All of
>     them generate
>     code. And some people have done some pretty crazy stuff with them
>     (especially
>     string mixins).
>
>     - Jonathan M Davis
>
>
> So is it like template metaprogramming in C++?  a small D example would
> be helpful.  There doesn't seem to be anything about it in TDPL.

Look up the index for "mixin". Most, if not all, examples of string 
mixins are generative.

The canonical example I give is std.bitmanip.bitfields, see 
http://www.dsource.org/projects/phobos/browser/trunk/phobos/std/bitmanip.d

> As for CTFE, does this mean I could call 'writeln()' at compile time and
> have it print a message to stdout while compiling?

You can't because that's not pure. Incidentally you can use pragma(msg, 
"hello") as an alternate mechanism. Helped a lot while debugging 
std.bitmanip.bitfields :o).


Andrei