C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  how i can write "operator+"?          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message av Guest Posted: Sat Jul 29, 2006 9:10 am    Post subject: how i can write "operator+"? i have my little string class, now i want do define something like this [ char *n="terza"; sstring a; a= "prima " + "seconda " + n; ] but for doing it i have to write sstream& operator+(char* a, char* b){} but compiler say something like "operator+(char*, char*) must be a member function or have a parameter of class type" how can i write a class type "string" that allow to write a= "prima " + "seconda " + n; above thank you Back to top Ian Collins Guest Posted: Sat Jul 29, 2006 9:10 am    Post subject: Re: how i can write "operator+"? av wrote: Quote: sstring operator+( const sstring& a, const sstring& b ) { sstring temp( a ); temp += b; return temp; } but temp should have the lifetime of operator+ this could be ok if it is "static" something like static sstring temp( a ); but in this case something strange have to happen in a = ((a="prima")+"s") + ((b="seconda")+"h"); but i have one simple solution for all this Please capitalise correctly. What exactly do you mean by "but temp should have the lifetime of operator+"? If I understand you correctly, it does and note operator+ returns by value. -- Ian Collins. Back to top Ian Collins Guest Posted: Sat Jul 29, 2006 9:10 am    Post subject: Re: how i can write "operator+"? av wrote: Quote: i have my little string class, now i want do define something like this [ char *n="terza"; sstring a; a= "prima " + "seconda " + n; ] but for doing it i have to write sstream& operator+(char* a, char* b){} Why sstream? Quote: but compiler say something like "operator+(char*, char*) must be a member function or have a parameter of class type" how can i write a class type "string" that allow to write a= "prima " + "seconda " + n; above thank you You can't. You could write sstring a = "prima "; a = a + "seconda " + n; Given the correct operators on sstring, but your code requires there to be an operator +() for const char* The common way to implement operator +() is to give your class a member operator +=() and use this in a non-member operator +(): class sstring { // stuff sstring& operator+=( const sstring& ); }; sstring operator+( const sstring& a, const sstring& b ) { sstring temp( a ); temp += b; return temp; } -- Ian Collins. Back to top Luc The Perverse Guest Posted: Sat Jul 29, 2006 9:10 am    Post subject: Re: how i can write "operator+"? "av" <av (AT) ala (DOT) a> wrote in message news:6g0mc211sbcjs2fan1tmtk8v6l9gog94mj (AT) 4ax (DOT) com... Quote: i have my little string class, now i want do define something like this [ char *n="terza"; sstring a; a= "prima " + "seconda " + n; ] but for doing it i have to write sstream& operator+(char* a, char* b){} but compiler say something like "operator+(char*, char*) must be a member function or have a parameter of class type" how can i write a class type "string" that allow to write a= "prima " + "seconda " + n; above thank you You can't over ride operators for primitives :) -- LTP :) Back to top av Guest Posted: Sat Jul 29, 2006 9:11 am    Post subject: Re: how i can write "operator+"? On Sat, 29 Jul 2006 18:44:01 +1200, Ian Collins wrote: Quote: av wrote: i have my little string class, now i want do define something like this [ char *n="terza"; sstring a; a= "prima " + "seconda " + n; ] but for doing it i have to write sstream& operator+(char* a, char* b){} Why sstream? but compiler say something like "operator+(char*, char*) must be a member function or have a parameter of class type" how can i write a class type "string" that allow to write a= "prima " + "seconda " + n; above thank you You can't. You could write sstring a = "prima "; a = a + "seconda " + n; Given the correct operators on sstring, but your code requires there to be an operator +() for const char* The common way to implement operator +() is to give your class a member operator +=() and use this in a non-member operator +(): class sstring { // stuff sstring& operator+=( const sstring& ); }; sstring operator+( const sstring& a, const sstring& b ) { sstring temp( a ); temp += b; return temp; } but temp should have the lifetime of operator+ this could be ok if it is "static" something like static sstring temp( a ); but in this case something strange have to happen in a = ((a="prima")+"s") + ((b="seconda")+"h"); but i have one simple solution for all this Back to top av Guest Posted: Sat Jul 29, 2006 9:11 am    Post subject: Re: how i can write "operator+"? On Sat, 29 Jul 2006 18:44:01 +1200, Ian Collins wrote: Quote: av wrote: i have my little string class, now i want do define something like this [ char *n="terza"; sstring a; a= "prima " + "seconda " + n; ] but for doing it i have to write sstream& operator+(char* a, char* b){} Why sstream? thank you to all, right the sstring above is wrong it should be sstream 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.