From -308374105286704736 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,fb1a92fa405c930c X-Google-Attributes: gidf78e5,public From: Lisa Lippincott Subject: Re: nested functions Date: 1999/06/23 Message-ID: <160619991237064992%lisa_lippincott@advisories.com>#1/1 X-Deja-AN: 492864317 Content-Transfer-Encoding: 8bit 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> Mail-Copies-To: poster X-Original-Date: Wed, 16 Jun 1999 12:37:06 -0700 Content-Type: text/plain; charset=ISO-8859-1 Organization: - X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBVAwUAN3CezqwEuYhIxRhxAQHdWwH7BcRFhHBgmRJtafDPz69pWTkQZD1y2OUu vZmEHNpodgiCCIpT4X0Ixs18u2X6LfZgPdMDhfMmbRtHrEG21Dlbxg== =jPAJ Mime-Version: 1.0 User-Agent: YA-NewsWatcher/4.2.2 Newsgroups: comp.std.c++ James Kanze asks: > 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. What you are describing would seem to be closure as > I understand it, but without the extended lifetime. There's a common meaning to all of these uses of "closure": a closure is a new function created by fixing some of the parameters to an existing function. Thus the one-parameter function "add three" is a closure of the two-parameter function "add." The confusion you express comes from interpreting "closure" in radically different environments. Lisp's rules of scope (functions may access objects defined in their callers) and lifetime (if it's accessible, it's alive) give Lisp's closures properties which seem bizzare from a C++ point of view. --Lisa Lippincott --- [ 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 ]