C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  C++ and C99 complex          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message skaller Guest Posted: Fri Aug 11, 2006 7:06 pm    Post subject: C++ and C99 complex Can someone explain the current and proposed relationship between C++ complex library type and C99 complex types? Its very unsatisfactory to have two distinct types for complex numbers. C++ complex is a template, and thus a class type. C99 complex may be a primitive type. If we wanted to make complex<double> the same type as C99 double _Complex, it would seem we'd need to allow a typedef as a specialisation, eg: typedef double _Complex template<> complex<double>; [unreadable .. I would write: typedef template<> complex<double> = double _Complex; if I could.] Is there another way? Is this possible? Any help here appreciated, including suggestions how to handle the dichotomy (apart from the obvious: convert one to the other as required) -- John Skaller <skaller at users dot sf dot net> Try Felix, the successor to C++ http://felix.sf.net --- [ 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://www.comeaucomputing.com/csc/faq.html ] Back to top P.J. Plauger Guest Posted: Sun Aug 13, 2006 1:37 am    Post subject: Re: C++ and C99 complex "skaller" <skaller (AT) users (DOT) sourceforge.net> wrote in message news:pan.2006.08.11.01.33.34.253488 (AT) users (DOT) sf.net... Quote: Can someone explain the current and proposed relationship between C++ complex library type and C99 complex types? Its very unsatisfactory to have two distinct types for complex numbers. C++ complex is a template, and thus a class type. C99 complex may be a primitive type. It may be unsatisfactory, but that's the way the two languages evolved. Quote: If we wanted to make complex<double> the same type as C99 double _Complex, it would seem we'd need to allow a typedef as a specialisation, eg: typedef double _Complex template<> complex<double>; [unreadable .. I would write: typedef template<> complex<double> = double _Complex; if I could.] Is there another way? Is this possible? Any help here appreciated, including suggestions how to handle the dichotomy (apart from the obvious: convert one to the other as required) We ensure that the two types have the same representation and are freely interchangeable in C++. That seems to solve most problems that occur when people call C99 complex functions with C++ complex objects. P.J. Plauger Dinkumware, Ltd. http://www.dinkumware.com --- [ 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://www.comeaucomputing.com/csc/faq.html ] Back to top skaller Guest Posted: Tue Aug 15, 2006 7:03 pm    Post subject: Re: C++ and C99 complex On Sat, 12 Aug 2006 20:37:52 +0000, P.J. Plauger wrote: Quote: "skaller" <skaller (AT) users (DOT) sourceforge.net> wrote in message news:pan.2006.08.11.01.33.34.253488 (AT) users (DOT) sf.net... Its very unsatisfactory to have two distinct types for complex numbers. C++ complex is a template, and thus a class type. C99 complex may be a primitive type. It may be unsatisfactory, but that's the way the two languages evolved. Well yes, I know that: different timing of the Standards and perhaps a failure of liaison. Quote: We ensure that the two types have the same representation and are freely interchangeable in C++. That seems to solve most problems that occur when people call C99 complex functions with C++ complex objects. I presume by 'we' you mean Dinkumware .. I guess I'm really asking if there is any proposal to do anything about it in the Standards committee .. (er.. used to call that the ANSI/ISO committee but it isn't ANSI anymore .. whats the right name for the 'committee as a whole' now?] My vague proposal for allowing a 'typedef to be a specialisation' was a suggestion that it might be possible to provide proper machinery to actually identify the types (in the case of a C++ library that actually does so). I admit I haven't thought much about whether the idea would actually work: but there is a motivation to think about it. Also, whether or not one library provides the same representation .. there is a question of which one to use, given one has an eye for the future: we're going to have 6 variants of, for example: sin z instead of just 3. Given that, suppose you wished to write some new functions .. what would you do? Use the C version? The C++ version? Both? Note that my typedef solution *precludes* doing both. If a typedef is used as a specialisation, then complex<float> and float _Complex will actually be the same type, which has implications for overloading. MAYBE the only thing that can be done is provide a macro which tells if these two types are representation compatible.. but this may still cause aliasing problems (see previous discussion where my assumptions aliasing pointers were quashed by aliasing rules). It's going to be a real pain if one has C libraries for complex arithmetic and also some C++ libraries: if the objects are matricies .. conversions would be too slow to contemplate. -- John Skaller <skaller at users dot sf dot net> Try Felix, the successor to C++ http://felix.sf.net --- [ 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://www.comeaucomputing.com/csc/faq.html ] Back to top kanze Guest Posted: Thu Aug 17, 2006 4:12 pm    Post subject: Re: C++ and C99 complex "P.J. Plauger" wrote: Quote: "skaller" <skaller (AT) users (DOT) sourceforge.net> wrote in message news:pan.2006.08.11.01.33.34.253488 (AT) users (DOT) sf.net... Can someone explain the current and proposed relationship between C++ complex library type and C99 complex types? Its very unsatisfactory to have two distinct types for complex numbers. C++ complex is a template, and thus a class type. C99 complex may be a primitive type. It may be unsatisfactory, but that's the way the two languages evolved. If we wanted to make complex<double> the same type as C99 double _Complex, it would seem we'd need to allow a typedef as a specialisation, eg: typedef double _Complex template<> complex<double>; [unreadable .. I would write: typedef template<> complex<double> = double _Complex; if I could.] Is there another way? Is this possible? Any help here appreciated, including suggestions how to handle the dichotomy (apart from the obvious: convert one to the other as required) We ensure that the two types have the same representation and are freely interchangeable in C++. When you say we, do you mean, "we, the members of the standardization committee", or "we, the implementors at Dinkumware"? (I know at one point there was a suggestion to constraint the implementation of complex<T>, so that it would be required to be physically equivalent of T[2]. I don't know what became of it, though.) Quote: That seems to solve most problems that occur when people call C99 complex functions with C++ complex objects. I presume that it does mean that you'd need something like: #ifdef __cplusplus extern "C" void f( std::complex< double > ) ; #else extern void f( double _Complex ) ; #endif in your header files, or... ? And of course, it would be preferable if said header file didn't include the C header <complex.h>, although that would be the natural thing for it to do if it were written by the developers of f() (who are working in C). -- James Kanze GABI Software Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 --- [ 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://www.comeaucomputing.com/csc/faq.html ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language, library and standards All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.