How to use span to wrap up command line args

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Is this use of the upcoming C++20 std::span correct and with no overhead to wrap up the command line arguments?

#include <iostream>
#include <span>

int main(int argc, const char* argv[])
{
    for (auto s : std::span { argv, static_cast<std::size_t>(argc) })
      std::cout << s << std::endl;
}

If it is correct, could I go futher and use with std::string_view?

std-span string-view c++20 c++
1 Answers

If you use () instead of {} you don't need the really verbose cast:

std::span(argv, argc)

This gives you a range of char const*. You can convert those to string_view using transform. This has some overhead because you need to do a bunch of strlens:

std::span(argv, argc)
    | std::views::transform([](char const* v){ return std::string_view(v); })

For stuff like this, I have a function object that performs casting, which is pretty easy to write, so this could be:

std::span(argv, argc)
    | std::views::transform(static_cast_<std::string_view>)
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