C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Limits of declaration syntax          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message John Nagle Guest Posted: Wed Dec 06, 2006 6:38 am    Post subject: Limits of declaration syntax This is valid, but requires typedefs. Can this return type be written in a single statement? Or does that exceed the capabilities of the declaration syntax? typedef char array3[3]; typedef array3& array3ref; array3ref foo(); John Nagle Animats --- [ 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 Greg Herlihy Guest Posted: Wed Dec 06, 2006 3:38 pm    Post subject: Re: Limits of declaration syntax John Nagle wrote: Quote: This is valid, but requires typedefs. Can this return type be written in a single statement? Or does that exceed the capabilities of the declaration syntax? typedef char array3[3]; typedef array3& array3ref; array3ref foo(); I'm not sure whether a valid declaration ever requires a typedef - though they can certainly help. I believe in this case the equivalent declaration without resorting to a typedef would be: char ( &foo() )[3]; Greg --- [ 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 t.y.c. Guest Posted: Wed Dec 06, 2006 3:38 pm    Post subject: Re: Limits of declaration syntax On Dec 6, 2:38 pm, John Nagle <n...@animats.com> wrote: Quote: This is valid, but requires typedefs. Can this return type be written in a single statement? Or does that exceed the capabilities of the declaration syntax? typedef char array3[3]; typedef array3& array3ref; array3ref foo(); You can do it as follow: typedef char (&array3ref)[3]; But I don't think this type is useful ^_^ , array3& is enough --- [ 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 Andrew Koenig Guest Posted: Wed Dec 06, 2006 3:39 pm    Post subject: Re: Limits of declaration syntax "John Nagle" <nagle (AT) animats (DOT) com> wrote in message news:pvpdh.19462$9v5.10796 (AT) newssvr29 (DOT) news.prodigy.net... Quote: This is valid, but requires typedefs. Can this return type be written in a single statement? Or does that exceed the capabilities of the declaration syntax? typedef char array3[3]; typedef array3& array3ref; array3ref foo(); charr (&foo())[3]; --- [ 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 James Dennett Guest Posted: Wed Dec 06, 2006 4:06 pm    Post subject: Re: Limits of declaration syntax John Nagle wrote: Quote: This is valid, but requires typedefs. Can this return type be written in a single statement? Or does that exceed the capabilities of the declaration syntax? typedef char array3[3]; typedef array3& array3ref; array3ref foo(); Looks nothing special to me, beyond the usual pathological nature of C++ declaration syntax: char array[3]; char (&foo())[3] { return array; } This compiles for me with Comeau C++ 4.3.3, and with g++ 3.3. (Of course it's clearer with suitable typedefs, and this is rather an odd case to want anyway, but the syntax allows it.) -- James --- [ 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 James Kanze Guest Posted: Wed Dec 06, 2006 4:08 pm    Post subject: Re: Limits of declaration syntax John Nagle wrote: Quote: This is valid, but requires typedefs. Can this return type be written in a single statement? Or does that exceed the capabilities of the declaration syntax? typedef char array3[3]; typedef array3& array3ref; array3ref foo(); char (&foo())[ 3 ] ; As usual, you start with what you want to declare: "foo". It's a function, so "foo()", which returns a reference "&foo()" to an array "&foo()[3]"---but the precedance is wrong, so we need parentheses "(&foo())[3]". And finally, char. I'll admit that it looks a little strange as a definition: char (&foo())[ 3 ] { // ... } Make it a const member function, and have the array contain pointers to member functions, and the syntax can become downright difficult. Something like the following (which declares a function taking an int as a parameter, and not a double): void (Bar::*(&Bar::foo( int i ) const)[ 3 ])( double d ) (To read, at least. Curiously, I find it easier to write the declarations. But what good is it to write such declarations, if you don't understand what they mean when you later read the code?) -- James Kanze (GABI Software) email:james.kanze (AT) gmail (DOT) com 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 Kristof Zelechovski Guest Posted: Mon Dec 11, 2006 1:18 am    Post subject: Re: Limits of declaration syntax Uzytkownik "Greg Herlihy" <greghe (AT) pacbell (DOT) net> napisal w wiadomosci news:1165409202.575999.37530 (AT) n67g2000cwd (DOT) googlegroups.com... Quote: John Nagle wrote: This is valid, but requires typedefs. Can this return type be written in a single statement? Or does that exceed the capabilities of the declaration syntax? typedef char array3[3]; typedef array3& array3ref; array3ref foo(); I'm not sure whether a valid declaration ever requires a typedef - operator char (&(void))[02], anyone? Chris --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. 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