Date: Wed, 28 Apr 2004 20:31:04 +0400 From: Sergey Zaharchenko <doublef@tele-kom.ru> To: Dag-Erling =?utf-8?B?U23QrHJncmF2?= <des@des.no> Cc: chat@freebsd.org Subject: Re: Beginning C++ in FreeBSD Message-ID: <20040428163104.GA10537@Shark.localdomain> In-Reply-To: <xzpfzao18gd.fsf@dwp.des.no> References: <20040425215837.3f4708fe.cpressey@catseye.mine.nu> <20040426094335.GA7578@online.fr> <20040426115842.GA4144@Shark.localdomain> <xzphdv5wq2q.fsf@dwp.des.no> <20040427160737.GA1325@Shark.localdomain> <xzpr7u918jv.fsf@dwp.des.no> <20040428023920.GA382@Shark.localdomain> <xzpfzao18gd.fsf@dwp.des.no>
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[-- Attachment #1 --] On Wed, Apr 28, 2004 at 04:30:10PM +0200, Dag-Erling SmЬrgrav probably wrote: > Sergey Zaharchenko <doublef@tele-kom.ru> writes: > > If the thesis sounds like > > > >> Any algorithm that can be written in one Turing-complete language can > >> be written in another Turing-complete language. > > > > then I think I understand it. > > No. A language is Turing-complete if it can be used to implement a > universal Turing machine. What you quote is merely a consequence of > Turing-completeness, not its definition. > OK. If I take out every word about main() from C's specification (making it an ordinary function), will the resulting `language' stay Turing-complete? If not, why? Is there an *algorithm* that I can write in C that I can't write in this derived language? (except that I have to run some of the functions of the resulting code from somewhere else). > > > In the functional way (`what it can do') C is not different from C++, as > > you all are pointing out (so I'm not trying to persuade you Turing was > > wrong). It's different in what it allows you to inform the system (the > > linker, for instance) about (and it will learn that *before* any actual > > algorithm of yours is executed). > > The operating system, the C++ compiler and the linker are all written > in C, and using C, you can write an emulator for the computer, on > which the OS, C++ compiler and linker will behave exactly as you > expect. > [ In fact, what I described is indeed intended to be a shared library, not a whole program... ] Within such emulation you will certainly be able to whatever you wish, including dynamically linking a library which has its own initialization in it (the constructor translated to C) to an executable. Fortunately, you don't have to do it. But how do you link a real executable against an emulated shared library:)? > DES > -- > Dag-Erling Sm?rgrav - des@des.no > -- DoubleF Everything is worth precisely as much as a belch, the difference being that a belch is more satisfying. -- Ingmar Bergman [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAj9xHwo7hT/9lVdwRAt8hAJ9r4OJGbCpWZrLZOVNcGi/h/7+LywCcDIdk g7LZkf4zyPAWWUoSgNS1JN4= =5wV7 -----END PGP SIGNATURE-----
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