From -823140775579592914 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,fb1a92fa405c930c X-Google-Attributes: gidf78e5,public From: Christopher Eltschka Subject: Re: nested functions Date: 1999/06/23 Message-ID: <37674DB8.B1128CB7@physik.tu-muenchen.de>#1/1 X-Deja-AN: 492870504 Content-Transfer-Encoding: 7bit Approved: Valentin Bonnard References: <7jd4c5$nup$1@nnrp1.deja.com> <7jjjr6$r02$1@nnrp1.deja.com> <7jma5c$i85@abyss.West.Sun.COM> <7jmdcv$a56$1@engnews1.eng.sun.com> <7jrqf5$op5$1@nnrp1.deja.com> <7jrv0r$dfq$1@engnews1.eng.sun.com> <7k5vjh$r0d$1@nnrp1.deja.com> X-Original-Date: Wed, 16 Jun 1999 09:09:44 +0200 X-Accept-Language: German/Germany, de-DE, German, de, en Content-Type: text/plain; charset=us-ascii Organization: [posted via] Leibniz-Rechenzentrum, Muenchen (Germany) X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBVAwUAN3Cnw6wEuYhIxRhxAQGwLgH/dEWMvi077/g885SmHs/xey1V1dU1NPsk Ny7OJl6uogVr7zllV5Rd2WLDLnEm7yDiNtTiK3srM2DeINVISm8m+Q== =R+B3 Mime-Version: 1.0 Newsgroups: comp.std.c++ James.Kanze@dresdner-bank.com wrote: > > In article <7jrv0r$dfq$1@engnews1.eng.sun.com>, > clamage@eng.sun.com (Steve Clamage) wrote: > > > C++ has enough different scope control mechanisms you don't need > > local functions the way you need them in, say, Pascal. The > > primary reason to have local functions in C++ would be to > > implement closures. If you just want to share state among > > cooperating functions, use a class. The code will be simpler > > and easier to maintain. > > Just a question of vocabulary, but what is a closure, exactly. I've > always thought that, in layman's terms, it extended the life of the > local context beyond the return from the function. I think that this is > how it works in lisp (but my lisp experience is limited to customizing > emacs, so I'm not sure). And of course, Borland has invented a totally > different meaning. Yes, that's a big problem. Maybe we should always qualify the word "closure", like "functional closure" and "BC++ closure". However, I prefer the term "bound member pointer" for the last one. (BTW, those "BC++ closures"/bound member pointers could be implemented as usual function pointers with the same trampoline technique as suggested for pointers to local functions - just that the trampoline would add the class pointer instead of the local function context). > What you are describing would seem to be closure as > I understand it, but without the extended lifetime. Or are you > suggesting that Pascal extended the lifetime of the function context > beyond the return from the function if the address of the function was > taken. (The Pascal I used didn't, but there are so many variations of > Pascal, it's hard to know what is standard, and what is fantasy on the > part of the implementer.) Just for your information: Standard Pascal doesn't allow to take the address of a function at all, nor does it let you return (or otherwise store) a reference to a function. All it allows is passing functions as parameters "by reference". So the question of surviving contexts doesn't arise at all here. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]