| |
| #include <boost/parameter.hpp> |
| #include <string> |
| |
| BOOST_PARAMETER_NAME(s1) |
| BOOST_PARAMETER_NAME(s2) |
| BOOST_PARAMETER_NAME(s3) |
| |
| template <typename ArgumentPack> |
| std::string f(ArgumentPack const& args) |
| { |
| std::string const& s1 = args[_s1]; |
| std::string const& s2 = args[_s2]; |
| typename boost::parameter::binding< |
| ArgumentPack,tag::s3,std::string |
| >::type s3 = args[_s3|(s1+s2)]; // always constructs s1+s2 |
| return s3; |
| } |
| |
| #include <boost/core/lightweight_test.hpp> |
| |
| int main() |
| { |
| std::string x = f((_s1="hello,", _s2=" world", _s3="hi world")); |
| BOOST_TEST_EQ(x, std::string("hi world")); |
| return boost::report_errors(); |
| } |
| |