// ---------------------------------------------------------------------------- // sample_formats.cpp : example of basic usage of format // ---------------------------------------------------------------------------- // Copyright Samuel Krempp 2003. Use, modification, and distribution are // subject to the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // See http://www.boost.org/libs/format for library home page // ---------------------------------------------------------------------------- #include #include #include #include "boost/format.hpp" // 2 custom namespaces, to bring in a few useful names : namespace MyNS_ForOutput { using std::cout; using std::cerr; using std::string; using std::endl; using std::flush; using boost::format; using boost::io::group; } namespace MyNS_Manips { using std::setfill; using std::setw; using std::hex ; using std::dec ; // gcc-2.95 doesnt define the next ones // using std::showbase ; // using std::left ; // using std::right ; // using std::internal ; } int main(){ using namespace MyNS_ForOutput; using namespace MyNS_Manips; std::cout << format("%|1$1| %|2$3|") % "Hello" % 3 << std::endl; // Reordering : cout << format("%1% %2% %3% %2% %1% \n") % "o" % "oo" % "O"; // 'simple' style. // prints "o oo O oo o \n" cout << format("(x,y) = (%1$+5d,%2$+5d) \n") % -23 % 35; // Posix-Printf style // No reordering : cout << format("writing %s, x=%s : %d-th step \n") % "toto" % 40.23 % 50; // prints "writing toto, x=40.23 : 50-th step \n" cout << format("(x,y) = (%+5d,%+5d) \n") % -23 % 35; cout << format("(x,y) = (%|+5|,%|+5|) \n") % -23 % 35; cout << format("(x,y) = (%|1$+5|,%|2$+5|) \n") % -23 % 35; // all those are the same, it prints "(x,y) = ( -23, +35) \n" // Using manipulators, via 'group' : cout << format("%2% %1% %2%\n") % 1 % group(setfill('X'), hex, setw(4), 16+3) ; // prints "XX13 1 XX13\n" // printf directives's type-flag can be used to pass formatting options : cout << format("_%1$4d_ is : _%1$#4x_, _%1$#4o_, and _%1$s_ by default\n") % 18; // prints "_ 18_ is : _0x12_, _ 022_, and _18_ by default\n" // Taking the string value : std::string s; s= str( format(" %d %d ") % 11 % 22 ); assert( s == " 11 22 "); // ----------------------------------------------- // %% prints '%' cout << format("%%##%#x ") % 20 << endl; // prints "%##0x14 " // ----------------------------------------------- // Enforcing the right number of arguments // Too much arguments will throw an exception when feeding the unwanted argument : try { format(" %1% %1% ") % 101 % 102; // the format-string refers to ONE argument, twice. not 2 arguments. // thus giving 2 arguments is an error } catch (boost::io::too_many_args& exc) { cerr << exc.what() << "\n\t\t***Dont worry, that was planned\n"; } // Too few arguments when requesting the result will also throw an exception : try { cerr << format(" %|3$| ") % 101; // even if %1$ and %2$ are not used, you should have given 3 arguments } catch (boost::io::too_few_args& exc) { cerr << exc.what() << "\n\t\t***Dont worry, that was planned\n"; } cerr << "\n\nEverything went OK, exiting. \n"; return 0; }