A C++17 (with GNU extensions) header-only named arguments library based on an idea from Richard Powell presented on CppCon 2018 “Named Arguments from Scratch”.
- Boost Hana
- GCC 8
- clang 7
Example:
#include <named_arguments.hpp>
#include <string>
#include <iostream>
using namespace named_arguments::literals;
float foo(int a, float&& b, std::string const& c){
return a + b * c.size();
};
auto bar = named_arguments::adapt(
foo,
"a"_default_arg = []{ return 10; },
"b"_no_default_arg,
"c"_default_arg = []{ return "string"; });
int main(){
auto v = bar("c"_arg = "string", "b"_arg = 0.5f);
std::cout << v << '\n';
}Use named_arguments::literals to import 3 user defined literals: "param_name"_default_arg, "param_name"_no_default_arg and "param_name"_arg.
Then you need a callable foo that you wrap into a new callable bar by named_arguments::adapt. The adapt call maps the parameters from its original call order to some parameter names. You can use "param_name"_no_default_arg if you just want to specify a name for the parameter or "param_name"_default_arg if you also want to set a default value. Default values must be specified by another callable without parameters! Most likly a lambda as in the example. This way the default value dosn't need to be copy- or movable. You must map all parameters, only a subset is invalid.
Then you can call bar by assign the values to its names. The names in a call must be declared with "param_name"_arg.
All parameters and the return value are perfect forwareded.
float v;
bar("b"_arg = std::move(v));
To build the unit tests you need CMake 3.12.4.
Build and exec tests with:
cd test
mkdir build
cd build
cmake ..
make
./simple_wrapThis software was originally developed privately by Benjamin Buch. All changes are released under the Boost Software License - Version 1.0 and published on GitHub.