C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Tools to generate operator<< and operator>> automatically?          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Frank Astier Guest Posted: Thu Nov 18, 2004 12:40 am    Post subject: Tools to generate operator<< and operator>> automatically? Hi - I am getting tired of writing and maintening operator<< and operator>> for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. I was wondering if there were some tools out there that could help? Thanks, Frank [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Daniel Krügler (ne Spange Guest Posted: Thu Nov 18, 2004 12:14 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall Hello Frank Astier, Frank Astier schrieb: Quote: Hi - I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. I was wondering if there were some tools out there that could help? The current boost 1.32 tarball at http://www.boost.org contains a very well designed serialization library. I would try that! (Side note: Actually the targeted release date for 1.32 should have been november, 17th. Is the current web site not up-to-date or are there some severe reasons for the delay?) Greetings from Bremen, Daniel Krügler [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jonathan Turkanis Guest Posted: Thu Nov 18, 2004 12:17 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall "Frank Astier" <fastier (AT) yahoo (DOT) com> wrote Quote: Hi - I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. I was wondering if there were some tools out there that could help? Emily winch wrote a paper about this: "Heterogeneous Lists of Named Objects" (see http://www.oonumerics.org/tmpw01/winch.pdf) Quoting from an introductory section: "There are many functions commonly forming part of class definitions that are normally written according to a simple set of rules, performing some operation on each member of the class in turn. These include operator==, operator=, operator<<, operator>>, destructors, and copy constructors. Storing the member variables of the class in a container makes it possible to use algorithms like those in the Standard Library to generate most of this code automatically. Members can then be added to the class without adding code to any of these functions." In the case of operator>> and operator<<, if you can give your class a container or tuple-like interface -- which need not be intrusive -- you can use my library Format Lite, at http://home.comcast.net/~jturkanis/format_lite/ For a description of how to give your class a tuple-like interface, see http://tinyurl.com/4gegk. Best Regards, Jonathan [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top jakacki Guest Posted: Thu Nov 18, 2004 12:22 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall Frank wrote: Quote: I am getting tired of writing and maintening operator and operator>> for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. I was wondering if there were some tools out there that could help? http://opencxx.sf.net BR Grzegorz -- Free C++ frontend library: http://opencxx.sourceforge.net China from the inside: http://www.staryhutong.com Myself: http://www.dziupla.net/gj/cv [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Michiel Salters Guest Posted: Fri Nov 19, 2004 12:52 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall [email]fastier (AT) yahoo (DOT) com[/email] (Frank Astier) wrote in message news:<40da7b0d.0411170850.6bf5e857 (AT) posting (DOT) google.com>... Quote: Hi - I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. Is it? How do you implement them given struct foo { string s1; string s2; }; Regards, Michiel Salters [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top fabioppp Guest Posted: Fri Nov 19, 2004 3:06 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall Frank Astier wrote: Quote: Hi - I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. I was wondering if there were some tools out there that could help? You need something like a reflection support! ...a compile time reflection maybe! template < typename class_type, typename field_type, field_type class_type::* ptom Quote: struct field { static const field_type& get(const class_type& base) { return base.*ptom; } }; struct nil {}; template struct fields { typedef head_ head; typedef tail_ tail; }; class Foo { int a; char b; typedef fields< field fields< field Quote: _fields; }; them you can write your generic serialization routine, which use CLASS::_fields --Fabio [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Frank Astier Guest Posted: Fri Nov 19, 2004 3:34 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall Guten Tag Daniel, Wie geht's? Quote: The current boost 1.32 tarball at http://www.boost.org contains a very well designed serialization library. I would try that! (Side note: Actually the targeted release date for 1.32 should have been november, 17th. Is the current web site not up-to-date or are there some severe reasons for the delay?) I'm afraid I missed the serialization library... I'm just coming back from their website, and I'm not sure which part of boost you are talking about. Could you tell me the precise name of the library? Thanks! Frank [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Brian Wood Guest Posted: Fri Nov 19, 2004 3:37 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall [email]fastier (AT) yahoo (DOT) com[/email] (Frank Astier) wrote in message news:<40da7b0d.0411170850.6bf5e857 (AT) posting (DOT) google.com>... Quote: Hi - I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. I was wondering if there were some tools out there that could help? Thanks, Frank Our site might be of interest to you. We do what you mentioned except we use Send/Receive functions rather than the <<, >> operators. Brian Wood Ebenezer Enterprises www.webebenezer.net [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Allan W Guest Posted: Fri Nov 19, 2004 4:09 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall [email]fastier (AT) yahoo (DOT) com[/email] (Frank Astier) wrote Quote: I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. What about private and protected members? What about integers or longs used as bitflags? What about enumerations? What about references? Quote: If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. For linked-list structures you'll end up dumping the rest of the list. For doubly-linked lists or lists with certain wrap-around characteristics, you'll dump members endlessly until you get a stack overflow. Quote: I was wondering if there were some tools out there that could help? Not familiar with any. Consider this (untested): template std::ostream & operator<<(std::ostream o,const T&t) { t.show(o); return o; } Now, define a const member function "show(std::ostream&)" in each of your classes, and you don't have to bother defining operator<< seperately. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jonathan Turkanis Guest Posted: Fri Nov 19, 2004 4:10 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall "Daniel Krügler (ne Spangenberg)" <dsp (AT) bdal (DOT) de> wrote: Quote: Frank Astier schrieb: I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. I was wondering if there were some tools out there that could help? The current boost 1.32 tarball at http://www.boost.org contains a very well designed serialization library. I would try that! I agree that the Boost Serialization library is an excellent choice for persistence, and I have heard from many people that it's easy to use. But AFAIK it does not provide an automated way to serialize the data members of a class -- you still have to write a serialize function in which you serialize the data members one at a time. It does, however, eliminate the problem of having to keep operator>> and operator<< in sync. Jonathan [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jeff Flinn Guest Posted: Sat Nov 20, 2004 10:34 am    Post subject: Re: Tools to generate operator<< and operator>> automaticall "Frank Astier" <fastier (AT) yahoo (DOT) com> wrote Quote: Guten Tag Daniel, Wie geht's? The current boost 1.32 tarball at http://www.boost.org contains a very well designed serialization library. I would try that! (Side note: Actually the targeted release date for 1.32 should have been november, 17th. Is the current web site not up-to-date or are there some severe reasons for the delay?) I'm afraid I missed the serialization library... I'm just coming back from their website, and I'm not sure which part of boost you are talking about. Could you tell me the precise name of the library? It's called 'serialization'. As Daniel stated it's part of the soon to be released 1.32 version. If you need it now you'll need to access the CVS repository at http://www.boost.org/more/getting_started.html#CVS Jeff Flinn [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Frank Astier Guest Posted: Sat Nov 20, 2004 6:15 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall I'm afraid I would be very naive, and just write: inline std::ostream& operator<<(std::ostream& out, const foo& f) { return out << s1 << endl << s2; } I'm curious about the pitfalls you can see in that naive approach? Thanks, Frank [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Frank Astier Guest Posted: Sat Nov 20, 2004 6:16 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall Quote: What about private and protected members? What about integers or longs used as bitflags? What about enumerations? What about references? For linked-list structures you'll end up dumping the rest of the list. For doubly-linked lists or lists with certain wrap-around characteristics, you'll dump members endlessly until you get a stack overflow. I think you are right: it's not gonna fly in the most general case. For the objects I work with though, maybe only part of the state can be isolated and persisted, maybe as a heterogeneous list of named objects: class Scenario : public VarListType<size_t, index, float, price, float, quantity, bool, allocation> { .... }; and somehow the VarListType would have generic operator<< and operator>>, and getters and setters so that I don't have to write those either, while we are at it. Frank [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top James Dennett Guest Posted: Sun Nov 21, 2004 6:52 am    Post subject: Re: Tools to generate operator<< and operator>> automaticall Frank Astier wrote: Quote: I'm afraid I would be very naive, and just write: inline std::ostream& operator<<(std::ostream& out, const foo& f) { return out << s1 << endl << s2; } I'm curious about the pitfalls you can see in that naive approach? Embedded newlines in s1 and/or s2 are the obvious problem there; there's no character you can be confident isn't used by one of the component (consider, for example, for case where one of your object's members itself uses the same approach). -- James [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Brian Wood Guest Posted: Mon Nov 22, 2004 11:03 pm    Post subject: Re: Tools to generate operator<< and operator>> automaticall [email]allan_w (AT) my-dejanews (DOT) com[/email] (Allan W) wrote in message news:<7f2735a5.0411180935.675d0607 (AT) posting (DOT) google.com>... Quote: fastier (AT) yahoo (DOT) com (Frank Astier) wrote I am getting tired of writing and maintening operator<< and operator for my objects, when the code in there seems to be really straightforward... and ready for automatic generation. I use those operators for persistence, and I just want all data members of my classes to get to/from the stream. What about private and protected members? I would approach it like this: Add function prototypes to the class and use our software to write the function implementations. As class members the functions have access to the private data. Quote: What about integers or longs used as bitflags? I'm not sure what you are getting at here. Quote: What about enumerations? What about references? If a data member is a pointer or an instance to another class, just call operator>> and operator<< on that class in turn. For linked-list structures you'll end up dumping the rest of the list. For doubly-linked lists or lists with certain wrap-around characteristics, you'll dump members endlessly until you get a stack overflow. We support the STL container classes, slist, and hash containers. Quote: I was wondering if there were some tools out there that could help? Not familiar with any. Consider this (untested): template std::ostream & operator<<(std::ostream o,const T&t) { t.show(o); return o; } Now, define a const member function "show(std::ostream&)" in each of your classes, and you don't have to bother defining operator<< seperately. Brian Wood Ebenezer Enterprises www.webebenezer.net [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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