Thought some people would find this interesting. http://www.comeaucomputing.com/iso/promises.html

"Golan Trevize" <golan.trevize@microoroo.com> wrote in message news:bs52pp$1iqp$1@digitaldaemon.com...
> Thought some people would find this interesting. http://www.comeaucomputing.com/iso/promises.html

Of course Greg Comeau would support export, since his EDG based compiler supports it and so it offers him a competitive advantage. <g>

Interestingly, D has 'export' automatically falling out of the semantics of how templates are defined in D.

Hi Walter,


"Walter" <walter@digitalmars.com> wrote in message news:bs541o$1kl8$1@digitaldaemon.com...
>
> "Golan Trevize" <golan.trevize@microoroo.com> wrote in message news:bs52pp$1iqp$1@digitaldaemon.com...
> > Thought some people would find this interesting. http://www.comeaucomputing.com/iso/promises.html
>
> Of course Greg Comeau would support export, since his EDG based compiler supports it and so it offers him a competitive advantage. <g>

Interesting that D has this.

I actually found the above reference in the OpenWatcom newsgoups.
Below is the post and it's quite interesting.
http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&selm=brla4v%241dm%241%40panix2.panix.com&rnum=11

> Interestingly, D has 'export' automatically falling out of the semantics
of
> how templates are defined in D.
>
>

GT

Golan Trevize wrote:
> Thought some people would find this interesting.
> http://www.comeaucomputing.com/iso/promises.html

I had just read it a few days ago. On the OpenWatcom newsgroup, someone advocated for export, i against, and was quite surprised to see Mr. Comeau answer!

I must say that i dislike him. He says something then something else and bends the meaning of each word as he sees fit. Just compare this letter to his post in the newsgroup, also mentioned somewhere down this thead.

The thing is, C++ module system is broken. And export doesn't fix it. I had posted Mathew an idea for fixing the module system, but with D and my lack of time to support anything, i don't think it's worth it. But if anything, it should work independantly of a compiler. If it finds use, someone may draw profit from integrating it into a front-end. But it would simply not work the other way around. Be it standard- backed or not.

Greg seems to want to get OpenWatcom team into working on export. This would clearly be a suicide for the project, since there are so many basic features not covered yet. And as i see there are none of the original developers among the crew. ;(

-eye

> The thing is, C++ module system is broken. And export doesn't fix it. I had posted Mathew an idea for fixing the module system, but with D and my lack of time to support anything, i don't think it's worth it.

Did you? I must confess I've forgotten what it was, and apologise for having done so.

Busy, busy, busy ...

Cheers

Matthew

P.S. If it was a good one, maybe I can put it in "More Imperfect C++" ;)

"Walter" <walter@digitalmars.com> wrote in message news:bs541o$1kl8$1@digitaldaemon.com...
> Of course Greg Comeau would support export, since his EDG based compiler supports it and so it offers him a competitive advantage. <g>

I must add to that that of course I am opposed to export because it apparently took EDG 3 man years of work to implement it, and I just don't see the return on investment for it. Export is a feature of enormous cost and very little benefit. But if I had export implemented in DMC++ I'd argue in favor of it <g>.

I'll also point out that nowhere does the article point out what the usefulness of export might be to programmers. I've yet to see any article make a compelling case for its advantages, especially in the light of its enormous cost. If someone knows of one, I'd appreciate a url!

"Golan Trevize" <golan.trevize@microoroo.com> wrote in message news:bs52pp$1iqp$1@digitaldaemon.com...
> Thought some people would find this interesting. http://www.comeaucomputing.com/iso/promises.html

Should contrast it with this paper on export: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1426.pdf

"Walter" <walter@digitalmars.com> wrote in message news:bs5mtu$2ijt$1@digitaldaemon.com...
>
> "Golan Trevize" <golan.trevize@microoroo.com> wrote in message news:bs52pp$1iqp$1@digitaldaemon.com...
> > Thought some people would find this interesting. http://www.comeaucomputing.com/iso/promises.html
>
> Should contrast it with this paper on export: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1426.pdf

Daveed Vandevoorde's rebuttal to n1426.pdf:

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=52f2f9cd .0305090607.62637fdf%40posting.google.com&rnum=1&prev=/groups%3Fq%3Ddaveed%2 Bvandevoorde%2Bmodule%2Bconcept%26ie%3DUTF-8%26oe%3DUTF-8%26hl%3Den

I haven't found any other substantive rebuttals while googling around.

Daveed says that the demand for export is based on desires for faster compilation speed and hiding template source code (much like source code is hidden when it's distributed as .obj or .lib files).

I'd like to see some benchmark results that show that export really does speed up compiles significantly. It sounds a lot like the justification for incremental linkers (Digital Mars' optlink can do full links faster than other vendors' linkers can do incremental links, which is why we never did an incremental linker). Hiding source could be easilly done by encrypting #include'd files in a manner that only the compiler could decrypt them (using well known public/private key cryptography).

That leaves Daveed's final argument for demand, that programmers are caught by assuming that templates can be treated like function bodies and separately compiled, and that export enables this to work. I don't see this as anything more than a minor misunderstanding on the programmer's part, one that is easilly corrected.

These seem to me to be weak justifications for the expense of export. Of course, I am not a member of the C++ committee and am not privy to the discussions they had about about export, if there is a better justification for it I'd sure like to see it.

I'm thoroughly underwhelmed by the whole notion of export.

But yet again, I may be partial, being the provider of an open-source suite of libraries that are 100% header-only.

:)



-- 
Matthew Wilson

STLSoft moderator (http://www.stlsoft.org)
Contributing editor, C/C++ Users Journal
(www.synesis.com.au/articles.html#columns)

"You can tell a Yorkshireman, but you can't tell him much!" -- Uncle Michael

----------------------------------------------------------------------------
---



"Walter" <walter@digitalmars.com> wrote in message news:bs5fr1$27mc$1@digitaldaemon.com...
>
> "Walter" <walter@digitalmars.com> wrote in message news:bs541o$1kl8$1@digitaldaemon.com...
> > Of course Greg Comeau would support export, since his EDG based compiler supports it and so it offers him a competitive advantage. <g>
>
> I must add to that that of course I am opposed to export because it apparently took EDG 3 man years of work to implement it, and I just don't see the return on investment for it. Export is a feature of enormous cost and very little benefit. But if I had export implemented in DMC++ I'd
argue
> in favor of it <g>.
>
> I'll also point out that nowhere does the article point out what the usefulness of export might be to programmers. I've yet to see any article make a compelling case for its advantages, especially in the light of its enormous cost. If someone knows of one, I'd appreciate a url!
>
>

In article <bs5t3j$2tvu$1@digitaldaemon.com>, Walter says...
>
>
>"Walter" <walter@digitalmars.com> wrote in message news:bs5mtu$2ijt$1@digitaldaemon.com...
>>
>> "Golan Trevize" <golan.trevize@microoroo.com> wrote in message news:bs52pp$1iqp$1@digitaldaemon.com...
>> > Thought some people would find this interesting. http://www.comeaucomputing.com/iso/promises.html
>>
>> Should contrast it with this paper on export: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1426.pdf

Having read these brings yet again to my mind that the C++ crowd still are the diametric opposite of Practical Programmers.

They seem constantly to take on challenges that you either have
to be superhuman or foolhardy to even consider. "Exportable
templates? Sure, bring 'em on!" What about consequences? Don't
you fear this'll break things, be impossible to implement, break
vendors' backs, or cause both vendors and users to deliberately
skip trying to hang on to the bleeding edge? "Aw, you know, there
are some amazing guys writing these compilers, they can pull off
just anything, in no time too." Do you _know_ that this is even
theoretically possible? "Naw, our vendors and programmers aren't
just ordinary folks. That kind of thing never stopped them before."
Oh, so you found the implications intractable, and just decided
to go ahead? "Let's not get snotty here!" Sorry. But shouldn't
language design follow similar paths as constructing a major
application?? "Um, I've got BS on the other line, gotta go, bye."

Bet they never heard of the KISS principle.

Boy, am I glad that we have Walter and D!