Uniprint

C++ Python-like print function with keyword arguments. Main idea of this thing is keyword arguments implementation in pure C++11.

To make things short, I'll give some code examples of Python's print function and compare it with Uniprint.

Python:

>>> print("Hello", "world", sep=', ', end='!\n')
Hello, world!
>>> print(1, 2, 3, sep='\n')
1
2
3
>>> from sys import stderr
>>> print("Message", file=stderr)
Message

C++ Uniprint:

uniprint::print print(std::cout);
using namespace uniprint::args;

print("Hello", "world", sep{", "}, end{"!\n"});
print(1, 2, 3, sep{"\n"});
print(file{std::cerr}, "Message"); // yep, kwarg before positional

Output:

Hello, world!
1
2
3
Message

So, does it look similar?

As I said earlier, the main idea of Uniprint is keyword arguments implementation in C++.

Uniprint also has flush and file arguments as the original print function.

How it is made

The implementation of Uniprint includes the gfp.hpp header. GFP means Get From Pack, and it does what it says: it takes the pack of values and extracts the values with specific types from it.

This is how it looks:

class print {
public:
  template <typename... Types> void operator()(Types &&...args) {
   // ...
     auto sep = gfp::get_from_pack<args::sep>{}(std::forward<Types>(args)...);

     gfp::call_match(
        sep,
        [&print_args](args::sep a) { print_args.sep = a.get(); },
        [](gfp::none_type) {}
     );
   // ...
  }
}

This code example is taken from the uniprint.hpp header. gfp::get_from_pack returns value of some (unknown) type, which is assigned to sep. Then the gfp::call_match is used to handle this value based on its type. If the type of sep is args::sep, then the separator's value is assigned to print_args.sep, otherwise (the type if sep is gfp::none_type) nothing happens. call_match calls the functor, which argument type matches the type of passed value.

This project is written just for fun, because I was wondering: "is it possible in C++?". The reason why it is written in C++11 is the same, because it was interesting to implement this without handy new tools like constexpr if and so on. It may be used in real-world projects, though I don't know, will it be a good idea.

Licensed under MIT License.