C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Re: Center formatted text with streams...          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Siemel Naran Guest Posted: Thu Jun 26, 2003 2:09 pm    Post subject: Re: Center formatted text with streams... "GRalphE" <vaghn (AT) yahoo (DOT) com> wrote in message Quote: If I turn on both left and right, would that produce centered text? No. Quote: Just a lame question. No. BTW, what should this do cout << myspace::center << "hello" << 3.0; Should the "hello" be centered then the 3.0 after it, or should "hello 3.0" be centered? Maybe you can write all the text you want centered into a string, then write a manipulator to center the string. There is no portable way to get the number of characters in a line. Let's assume it is 80, though perhaps you can use a non-portable function to get it like gettextinfo in Windows. cout << myspace::center(ostringstream() << "hello" << 3.0); where class center { public: center(ostream& text); // may throw bad_cast private: ostringstream& d_text; }; ostream& operator<<(ostream& out, center c) { const int screenwidth = 80; const string& text = d_text.str(); const int textwidth = int(text.size()); int space = (screenwidth - textwidth) / 2; if (space < 0) space = 0; out.setfill(' '); out << setw(space) << "" << text << 'n'; return out; } -- +++++++++++ Siemel Naran [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Siemel Naran Guest Posted: Thu Jun 26, 2003 2:24 pm    Post subject: Re: Center formatted text with streams... "GRalphE" <vaghn (AT) yahoo (DOT) com> wrote in message Quote: If I turn on both left and right, would that produce centered text? No. Quote: Just a lame question. No. BTW, what should this do cout << myspace::center << "hello" << 3.0; Should the "hello" be centered then the 3.0 after it, or should "hello 3.0" be centered? Maybe you can write all the text you want centered into a string, then write a manipulator to center the string. There is no portable way to get the number of characters in a line. Let's assume it is 80, though perhaps you can use a non-portable function to get it. cout << myspace::center(ostringstream() << "hello" << 3.0); where class center { public: center(ostream& text); // may throw bad_cast private: ostringstream& d_text; }; ostream& operator<<(ostream& out, center c) { const int screenwidth = 80; const string& text = d_text.str(); const int textwidth = int(text.size()); int space = (screenwidth - textwidth) / 2; if (space < 0) space = 0; out.setfill(' '); out << setw(space) << text << 'n'; return out; } -- +++++++++++ Siemel Naran [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Maciej Sobczak Guest Posted: Thu Jun 26, 2003 7:39 pm    Post subject: Re: Center formatted text with streams... Hi, Siemel Naran wrote: Quote: cout << myspace::center(ostringstream() << "hello" << 3.0); Except that ostringstream() above will create a temporary and the first operator<< (the one on the right of ostringstream) is non-member function accepting non-const reference to its left parameter. It is not possible to bound temporaries to non-const references. In other words, it is not possible to use temporary stream to insert a string into it. Funny: you can insert numeric values this way with no problem. Even more fun: ostringstream() << "hello" << 3; // error for the reasons above ostringstream() << 3 << "hello"; // OK -- Maciej Sobczak http://www.maciejsobczak.com/ Distributed programming lib for C, C++, Python & Tcl: http://www.maciejsobczak.com/prog/yami/ [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top John Potter Guest Posted: Fri Jun 27, 2003 4:44 pm    Post subject: Re: Center formatted text with streams... On 26 Jun 2003 10:24:12 -0400, "Siemel Naran" <SiemelNaran (AT) KILL (DOT) att.net> wrote: Quote: BTW, what should this do cout << myspace::center << "hello" << 3.0; Should the "hello" be centered then the 3.0 after it, or should "hello 3.0" be centered? It should produce "hello3" because the width is 0 for both items. Padding makes no sense without a setw. cout << myspace::center << setw(9) << "hello" << setw( << 3.0 would give " hello 3 ". Note that it is sticky like all formatters. How do you clear it? John [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top John Potter Guest Posted: Fri Jun 27, 2003 4:45 pm    Post subject: Re: Center formatted text with streams... On 26 Jun 2003 15:39:43 -0400, Maciej Sobczak <maciej (AT) maciejsobczak (DOT) com> wrote: Quote: ostringstream() << "hello" << 3; // error for the reasons above You just need to know how to cheat. ostringstream() << flush << "hello" << 3; John [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top llewelly Guest Posted: Sat Jun 28, 2003 11:32 pm    Post subject: Re: Center formatted text with streams... "Siemel Naran" <SiemelNaran (AT) KILL (DOT) att.net> writes: Quote: "Maciej Sobczak" <maciej (AT) maciejsobczak (DOT) com> wrote in message cout << myspace::center(ostringstream() << "hello" << 3.0); Except that ostringstream() above will create a temporary and the first operator<< (the one on the right of ostringstream) is non-member function accepting non-const reference to its left parameter. It is not possible to bound temporaries to non-const references. Good point. You can have center's constructor center::center(const std::string&). Or you can write a class my_ostringstream that holds an ostringstream or derives from one, and write a member template operator<<. class my_ostringstream : public std::ostringstream { public: template my_ostringstream& operator<<(const T& arg) const { std::ostringstream << arg; return *this; } }; The center's constructor can take a my_ostringstream& as an argument and there's no need for dynamic_cast. In other words, it is not possible to use temporary stream to insert a string into it. Funny: you can insert numeric values this way with no problem. Even more fun: ostringstream() << "hello" << 3; // error for the reasons above ostringstream() << 3 << "hello"; // OK Why is the 2nd one OK? Because you can pass a temporary to a non-const member function. However you cannot bind a temporary to a reference to non-const. More unecessary incompatibility between member and non-member functions. More reason to prefer non-member functions to member functions, wherever reasonable. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top kanze@gabi-soft.fr Guest Posted: Mon Jun 30, 2003 4:04 pm    Post subject: Re: Center formatted text with streams... John Potter <jpotter (AT) falcon (DOT) lhup.edu> wrote Quote: On 26 Jun 2003 10:24:12 -0400, "Siemel Naran" [email]SiemelNaran (AT) KILL (DOT) att.net[/email] wrote: BTW, what should this do cout << myspace::center << "hello" << 3.0; Should the "hello" be centered then the 3.0 after it, or should "hello 3.0" be centered? It should produce "hello3" because the width is 0 for both items. Padding makes no sense without a setw. cout << myspace::center << setw(9) << "hello" << setw( << 3.0 would give " hello 3 ". Note that it is sticky like all formatters. How do you clear it? The same way you clear ios::left and ios::right ? -- James Kanze GABI Software mailto:kanze (AT) gabi-soft (DOT) fr Conseils en informatique orientée objet/ http://www.gabi-soft.fr Beratung in objektorientierter Datenverarbeitung 11 rue de Rambouillet, 78460 Chevreuse, France, Tél. : +33 (0)1 30 23 45 16 [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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