From -4079414850451473743 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,a69618ea97f65037 X-Google-Attributes: gidf78e5,public From: Christopher Eltschka Subject: Re: nested functions Date: 1998/05/04 Message-ID: <354DC34A.37280BCE@physik.tu-muenchen.de>#1/1 X-Deja-AN: 351026238 Content-Transfer-Encoding: 7bit Approved: stephen.clamage@sun.com (comp.std.c++) References: <6hac23$8lb$1@news2.isdnet.net> <353b85b9.0@news.iprolink.ch> <35459993.3BC581B0@physik.tu-muenchen.de> <199804281743.NAA18001@calumny.jyacc.com> <35472A6D.562EA04C@physik.tu-muenchen.de> Mime-Version: 1.0 Originator: clamage@taumet X-Nntp-Posting-Host: coulomb.t30.physik.tu-muenchen.de X-UID: 0000000001 X-Status: $$$T Content-Type: text/plain; charset=us-ascii Organization: [posted via] Leibniz-Rechenzentrum, Muenchen (Germany) Newsgroups: comp.std.c++ Hyman Rosen wrote: > > Christopher Eltschka writes: > > But as long as f didn't return, you don't need a closure mechanism, > > as the usual nested function mechanism would work well. > > Perhaps I am misusing the term closure? I understand a closure to be the > combination of a function pointer plus a set of stack frame pointers, one > for each static nesting level of the pointed-to function. What do you mean > by it? Are Scheme closures different? In Scheme, automatic variables can > outlive the exit from their scope, but that's because Scheme is a garbage > collected language. Java now has the same sort of thing. Maybe my understanding of the term "closure" is wrong. The posting which introduced the term to the thread spoke about "true closures" with an example where the function context outlives the return, and the behaviour of the program demonstrated just this by creating two such contexts. Also it mentioned the gcc model as not being "true closures". Therefore I concluded that closures are function contexts which "survive" the return of the function (which makes sense as those contexts are in some way "closed" by the return: they cannot be accessed directly any more, but only indirectly by the local functions). BTW, you don't need a frame pointer for each nesting level. You just need one for the level below. From there, you can get to the other levels sequencially. [ 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 ]