C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  struct constructor          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message slurper Guest Posted: Tue Dec 30, 2003 12:34 am    Post subject: struct constructor hi, i'm studying some stl. i saw the pair implementation in a header-file but what i wonder is if a struct can have constructors as it seems in following snippet from the stl library. the snippets i wonder about are indicated with --------> : i thought a struct doesn't have constructors (but here there are four, actually three) template <class _T1, class _T2> struct pair { typedef _T1 first_type; typedef _T2 second_type; _T1 first; _T2 second; #ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS ---------> pair() : first(), second() {} #else ---------> pair() : first(_T1()), second(_T2()) {} #endif ---------> pair(const _T1& __a, const _T2& __b) : first(__a), second(__b) {} template <class _U1, class _U2> --------> pair(const pair<_U1, _U2>& __p) : first(__p.first), second(__p.second) {} }; Back to top Cy Edmunds Guest Posted: Tue Dec 30, 2003 1:02 am    Post subject: Re: struct constructor "slurper" <slurper1234 (AT) hotmail (DOT) com> wrote Quote: hi, i'm studying some stl. i saw the pair implementation in a header-file but what i wonder is if a struct can have constructors as it seems in following snippet from the stl library. the snippets i wonder about are indicated with --------> : i thought a struct doesn't have constructors (but here there are four, actually three) [snip] In C++, the only difference between a struct and a class is that all members of a struct are public by default. Thus a struct can have a constructor or anything else a class can have. -- Cy http://home.rochester.rr.com/cyhome/ Back to top Ron Natalie Guest Posted: Tue Dec 30, 2003 1:02 am    Post subject: Re: struct constructor "slurper" <slurper1234 (AT) hotmail (DOT) com> wrote Quote: hi, i'm studying some stl. i saw the pair implementation in a header-file but what i wonder is if a struct can have constructors as it seems in following snippet from the stl library. the snippets i wonder about are indicated with --------> : i thought a struct doesn't have constructors (but here there are four, actually three) You thought wrong. Structs are classes. The only difference is that classes defined with the struct keyword have public access by default. Classes defined with the class keyword have private access by default. That is: struct x { .... }; is the same as: class x { public: ... } ; Back to top Nick Hounsome Guest Posted: Tue Dec 30, 2003 9:11 am    Post subject: Re: struct constructor "Cy Edmunds" <cedmunds (AT) spamless (DOT) rochester.rr.com> wrote Quote: "slurper" <slurper1234 (AT) hotmail (DOT) com> wrote in message news:3ff0c83f$0$20545$ba620e4c (AT) news (DOT) skynet.be... hi, i'm studying some stl. i saw the pair implementation in a header-file but what i wonder is if a struct can have constructors as it seems in following snippet from the stl library. the snippets i wonder about are indicated with --------> : i thought a struct doesn't have constructors (but here there are four, actually three) [snip] In C++, the only difference between a struct and a class is that all members of a struct are public by default. Thus a struct can have a constructor or anything else a class can have. I suspect that the poster was thinking that struct = POD (plain old (C compatible) data). Of course this isn't true but what may need pointing out is that even POD can have some C++ stuff such as ctors and member functions. Off the top of my head the only things it can't have (and still be POD) are: - access specifiers - virtual methods - destructor - references - any member that isn't POD There may also be restrictions on ctors Quote: -- Cy http://home.rochester.rr.com/cyhome/ Back to top David White Guest Posted: Tue Dec 30, 2003 9:53 am    Post subject: Re: struct constructor "Cy Edmunds" <cedmunds (AT) spamless (DOT) rochester.rr.com> wrote Quote: "slurper" <slurper1234 (AT) hotmail (DOT) com> wrote in message news:3ff0c83f$0$20545$ba620e4c (AT) news (DOT) skynet.be... hi, i'm studying some stl. i saw the pair implementation in a header-file but what i wonder is if a struct can have constructors as it seems in following snippet from the stl library. the snippets i wonder about are indicated with --------> : i thought a struct doesn't have constructors (but here there are four, actually three) [snip] In C++, the only difference between a struct and a class is that all members of a struct are public by default. And public inheritance by default (as against private for classes). DW Back to top Martijn Lievaart Guest Posted: Tue Dec 30, 2003 10:40 am    Post subject: Re: struct constructor On Mon, 29 Dec 2003 20:02:20 -0500, Ron Natalie wrote: Quote: You thought wrong. Structs are classes. The only difference is that classes defined with the struct keyword have public access by default. Classes defined with the class keyword have private access by default. s/access/access and inheritance/g HTH, M4 Back to top Ron Natalie Guest Posted: Tue Dec 30, 2003 2:40 pm    Post subject: Re: struct constructor "Nick Hounsome" <nh002 (AT) blueyonder (DOT) co.uk> wrote Quote: - destructor User declared constructors, destructors, or copy-assignment operators. Quote: - references - any member that isn't POD non-static members of reference or other non-pod type. Back to top Ron Natalie Guest Posted: Tue Dec 30, 2003 2:44 pm    Post subject: Re: struct constructor "Martijn Lievaart" <m (AT) remove (DOT) this.part.rtij.nl> wrote Quote: On Mon, 29 Dec 2003 20:02:20 -0500, Ron Natalie wrote: You thought wrong. Structs are classes. The only difference is that classes defined with the struct keyword have public access by default. Classes defined with the class keyword have private access by default. s/access/access and inheritance/g Sorry, my statement is right as it stands. I didn't say anything that limits the access control to members. Access refers to both members and base classes. Inheritance only exists in the concept of name lookup. Back to top Martijn Lievaart Guest Posted: Tue Dec 30, 2003 3:24 pm    Post subject: Re: struct constructor On Tue, 30 Dec 2003 09:44:08 -0500, Ron Natalie wrote: Quote: "Martijn Lievaart" <m (AT) remove (DOT) this.part.rtij.nl> wrote in message news:pan.2003.12.30.10.40.06.338650 (AT) remove (DOT) this.part.rtij.nl... On Mon, 29 Dec 2003 20:02:20 -0500, Ron Natalie wrote: You thought wrong. Structs are classes. The only difference is that classes defined with the struct keyword have public access by default. Classes defined with the class keyword have private access by default. s/access/access and inheritance/g Sorry, my statement is right as it stands. I didn't say anything that limits the access control to members. Access refers to both members and base classes. Inheritance only exists in the concept of name lookup. Yes, now you mention it, but I think that explicitly stating it applies to inheritance as well makes it clearer. I don't think everyone will immediately come your (correct) interpretation. I know I didn't. :-) M4 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 (comp.lang.c++) 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.