C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  separation of pointer types          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message christopher diggins Guest Posted: Mon Apr 11, 2005 11:23 pm    Post subject: separation of pointer types What is currently referred to as a pointer in C++ is in my opinion several different types inappropriately amalgamated as one. Consider how there are four very clear categories of pointers with entirely different interfaces: 1) the result of an address-of operation - supports indirection - supports comparison - increment/decrement undefined - delete undefined - delete[] undefined 2) reference to an element of an array - supports indirection - supports comparison - supports increment/decrement - delete undefined - delete[] undefined 3) reference to a dynamically allocated array - supports indirection - supports comparison - supports delete[] - delete undefined 4) reference to a dynamically allocated object - supports indirection - supports comparison - delete[] undefined - supports delete I see no reason these four cases should not each have a separate type. Does anyone else find the the hypothetical idea of separation of pointers into different types to have some allure? -- Christopher Diggins Object Oriented Template Library (OOTL) http://www.ootl.org --- [ 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.jamesd.demon.co.uk/csc/faq.html ] Back to top Andrew Koenig Guest Posted: Wed Apr 13, 2005 5:53 am    Post subject: Re: separation of pointer types ""christopher diggins"" <cdiggins (AT) videotron (DOT) ca> wrote Quote: I see no reason these four cases should not each have a separate type. Does anyone else find the the hypothetical idea of separation of pointers into different types to have some allure? Does that mean that whenever I write a function that takes a pointer argument, and that function does only things with the pointer that all four of your desired categories support, that I must overload the function for each category anyway? --- [ 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.jamesd.demon.co.uk/csc/faq.html ] Back to top christopher diggins Guest Posted: Thu Apr 14, 2005 5:07 am    Post subject: Re: separation of pointer types ""Andrew Koenig"" <ark (AT) acm (DOT) org> wrote Quote: ""christopher diggins"" <cdiggins (AT) videotron (DOT) ca> wrote in message news:xiy6e.58852$wl6.549361 (AT) weber (DOT) videotron.net... I see no reason these four cases should not each have a separate type. Does anyone else find the the hypothetical idea of separation of pointers into different types to have some allure? Does that mean that whenever I write a function that takes a pointer argument, and that function does only things with the pointer that all four of your desired categories support, that I must overload the function for each category anyway? All four categories overlap only with regards to indirection. This means that the appropirate type would be a reference. -- Christopher Diggins Object Oriented Template Library (OOTL) http://www.ootl.org --- [ 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.jamesd.demon.co.uk/csc/faq.html ] Back to top Marc Schoolderman Guest Posted: Fri Apr 15, 2005 4:46 am    Post subject: Re: separation of pointer types christopher diggins wrote: Quote: All four categories overlap only with regards to indirection. This means that the appropirate type would be a reference. No. As was debated over and over in a recent thread, a reference can't be "null", whereas a pointer can. Also, a pointer can be changed inside the function, whereas a reference can't. So this isn't equivalent. A more fundamental problem has to do with the low-level nature of pointers. IMHO, they're not supposed to be some "pure" error-proof language construct for the things you're suggesting, they're "just above the machine level" abstractions for addresses, and the things you use addresses for in machine language. Having four different pointer types for the same low-level construct would be extremely confusing. ~Marc --- [ 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.jamesd.demon.co.uk/csc/faq.html ] Back to top Victor Bazarov Guest Posted: Fri Apr 15, 2005 4:47 am    Post subject: Re: separation of pointer types christopher diggins wrote: Quote: ""Andrew Koenig"" <ark (AT) acm (DOT) org> wrote in message news:G9Q6e.564825$w62.517033 (AT) bgtnsc05-news (DOT) ops.worldnet.att.net... ""christopher diggins"" <cdiggins (AT) videotron (DOT) ca> wrote in message news:xiy6e.58852$wl6.549361 (AT) weber (DOT) videotron.net... I see no reason these four cases should not each have a separate type. Does anyone else find the the hypothetical idea of separation of pointers into different types to have some allure? Does that mean that whenever I write a function that takes a pointer argument, and that function does only things with the pointer that all four of your desired categories support, that I must overload the function for each category anyway? All four categories overlap only with regards to indirection. This means that the appropirate type would be a reference. I don't see how this could coexist with a notion of 'null pointer value' (a pointer that is valid yet does not point to any object). V --- [ 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.jamesd.demon.co.uk/csc/faq.html ] Back to top kuyper@wizard.net Guest Posted: Fri Apr 15, 2005 4:50 am    Post subject: Re: separation of pointer types "christopher diggins" wrote: .. Quote: All four categories overlap only with regards to indirection. This means that the appropirate type would be a reference. All four type support indirection, comparison, and increment. References only support indirection. --- [ 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.jamesd.demon.co.uk/csc/faq.html ] Back to top christopher diggins Guest Posted: Sat Apr 16, 2005 10:30 pm    Post subject: Re: separation of pointer types "Marc Schoolderman" <squell (AT) alumina (DOT) nl> wrote Quote: christopher diggins wrote: All four categories overlap only with regards to indirection. This means that the appropirate type would be a reference. No. As was debated over and over in a recent thread, a reference can't be "null", whereas a pointer can. You are correct. All four categories do support comparison to null. Quote: Also, a pointer can be changed inside the function, whereas a reference can't. You are correct here as well. Quote: So this isn't equivalent. I stand corrected. In the end, though I still stand by my thesis that four separate pointer classes can and probably should be used to replace the four different categories of usage of regular pointers in most applications. Quote: A more fundamental problem has to do with the low-level nature of pointers. IMHO, they're not supposed to be some "pure" error-proof language construct for the things you're suggesting, they're "just above the machine level" abstractions for addresses, Exactly! My point is programmers far too frequently just use pointers when something more abstract would be more appropriate. Quote: and the things you use addresses for in machine language. Having four different pointer types for the same low-level construct would be extremely confusing. So we agree using pointers is neccessary when we need the low-level construct. I am simply saying that in most applications it is more appropriate to use a more accurate abstraction instead. Quote: ~Marc Christopher --- [ 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.jamesd.demon.co.uk/csc/faq.html ] Back to top Bob Bell Guest Posted: Tue Apr 19, 2005 12:32 am    Post subject: Re: separation of pointer types "christopher diggins" wrote: Quote: "Marc Schoolderman" <squell (AT) alumina (DOT) nl> wrote in message news:425E6DE0.7050206 (AT) alumina (DOT) nl... So this isn't equivalent. I stand corrected. In the end, though I still stand by my thesis that four separate pointer classes can and probably should be used to replace the four different categories of usage of regular pointers in most applications. So what about Andrew's question: do I need to overload functions four times four the four kinds of pointers? Bob --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. 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