C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  enum, Why does C++ still keep the ugly C feature          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message Guest Posted: Thu Apr 06, 2006 7:06 am    Post subject: enum, Why does C++ still keep the ugly C feature enum X{a, b, c}; X i = a; a, b, c and X are in a same scope. why? and now, I can't do it like this struct cost_form_Beijing { enum airplane{London, Rome, Berlin}; enum train{London = 100, Rome, Berlin}; }; and I don't like fixed it but what I only can do in this way. struct cost_form_Chongqing { struct airplane { const static int London = 0; const static int Rome = 1; const static int Berlin = 2; }; struct train { const static int London = 100; const static int Rome = 101; const static int Berlin = 102; }; }; in this way, a big problem is the type of train::London is int, not train...so I would like this and I think this feature should be introduced into C++ enum X{a, b, c}; X i = X::a; --- [ 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 Rolf Magnus Guest Posted: Thu Apr 06, 2006 3:06 pm    Post subject: Re: enum, Why does C++ still keep the ugly C feature cnjinhao (AT) hotmail (DOT) com wrote: Quote: and I don't like fixed it but what I only can do in this way. struct cost_form_Chongqing { struct airplane { const static int London = 0; const static int Rome = 1; const static int Berlin = 2; }; struct train { const static int London = 100; const static int Rome = 101; const static int Berlin = 102; }; }; in this way, a big problem is the type of train::London is int, not train...so How about this: struct airplane { enum ap { London, Rome, Berlin }; airplane(ap arg) : value_(arg) {} operator int() { return value_; } private: ap value_; }; int main() { airplane a = airplane::London; } --- [ 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 Zara Guest Posted: Thu Apr 06, 2006 3:06 pm    Post subject: Re: enum, Why does C++ still keep the ugly C feature On 6 Apr 2006 06:20:02 GMT, cnjinhao (AT) hotmail (DOT) com wrote: Quote: enum X{a, b, c}; X i = a; a, b, c and X are in a same scope. why? and now, I can't do it like this struct cost_form_Beijing { enum airplane{London, Rome, Berlin}; enum train{London = 100, Rome, Berlin}; }; and I don't like fixed it but what I only can do in this way. <..> You may separate by concept: namespace by_train { enum destination {London,Rome,Berlin}; } namespace by_plane { enum destination {London,Rome,Berlin}; } Now you may refer to a destination specifying also the means, so you are really refering to the travel itself: by_train::London by_plane::London Which makes both a separation of the underlying concepts and and easy to spot meaning of the value Best regards, Zara --- [ 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 Hyman Rosen Guest Posted: Thu Apr 06, 2006 3:06 pm    Post subject: Re: enum, Why does C++ still keep the ugly C feature cnjinhao (AT) hotmail (DOT) com wrote: Quote: I would like this and I think this feature should be introduced into C++ enum X{a, b, c}; X i = X::a; namespace X { enum e { a, b, c }; } X::e i = X::a; or struct cost_form_Beijing { struct airplane { enum e {London, Rome, Berlin}; }; struct train { enum e {London = 100, Rome, Berlin} }; }; A drop more typing, and the enum type is name::e instead of just name, but it's not that onerous, and it stays compatible with C. --- [ 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 Guest Posted: Fri Apr 07, 2006 5:06 am    Post subject: Re: enum, Why does C++ still keep the ugly C feature thanks for your thread namespace X { enum e { a, b, c }; } X::e i = X::a; what i expect is X::e i = X::e::a; a, b, c all are in {}, so, they should be in a scope of e. in my opinion, it is really a ugly feature that elements of a enum are in a same scope of their enum --- [ 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 Seungbeom Kim Guest Posted: Sat Apr 08, 2006 2:06 am    Post subject: Re: enum, Why does C++ still keep the ugly C feature cnjinhao (AT) hotmail (DOT) com wrote: Quote: thanks for your thread namespace X { enum e { a, b, c }; } X::e i = X::a; what i expect is X::e i = X::e::a; a, b, c all are in {}, so, they should be in a scope of e. in my opinion, it is really a ugly feature that elements of a enum are in a same scope of their enum You raised a problem, and Hyman suggested a workaround. What's the problem with the suggested workaround? The status quo may not be the most elegant design choice, but it is what we have now and what lots of existing codes depend on. You are free to insist on a change of the language definition, but just don't expect it to be accepted easily, especially when there's an easy workaround. -- Seungbeom Kim --- [ 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 SuperKoko Guest Posted: Fri Apr 14, 2006 8:06 am    Post subject: Re: enum, Why does C++ still keep the ugly C feature Here is a complete solution: struct cost_form_Beijing { struct airplane { enum airplane_t {London, Rome, Berlin}; }; typedef airplane::airplane_t airplane_t; struct train { enum train_t {London = 100, Rome, Berlin}; }; typedef train::train_t train_t; }; int main() { cost_form_Beijing::airplane_t airp=cost_form_Beijing::airplane::London; } The only flaw is the fact that the type of the enumeration is now airplane_t, while the scope used to access the enumeration items is airplane. And compatibility with C is maintained. Note : a typedef can't be used to access scope of the aliased type. --- [ 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.