Feature converter ints doubles

[sbearrows]

Might better to name them as_doubles() and as_integers() to differentiate from scalar double and int?? When I first was making it that sounded odd to me but now I'm not so convinced.

fixes #46

[jimhester]

I think you are right, as_doubles() and as_integers() seems like a good idea to me.

[jimhester]

Looks like you have a blank newline that is causing the format_check job to fail https://github.com/r-lib/cpp11/pull/201/checks?check_run_id=3024080555#step:5:11.

FWIW in RStudio you can enable showing whitespace characters with

Tools -> Global Options -> Code -> Display, check "Show whitespace characters".

Which could help spot these more easily.

[sbearrows]

Okay I'm going to make those changes to function names. Any insights you might have on the ubuntu 3.4 error? I can't really tell where or why it's occurring.

[jimhester]

I was able to reproduce it locally with R 3.4, it seems like an issue related to cpp11::stop(). That function requires unwind_protect, which IIRC has some issues on R versions before 3.5.

Switching the errors to throw regular C++ exceptions instead fixes the test failures.

I think it might be worth changing all the uses of cpp11::stop() in the cpp11 code to throw exceptions instead. In general I think cpp11:stop() seems to work fine for user code, but perhaps it would be better for the internal cpp11 code not to rely on it.

[jimhester]

cpp11 defines a type_error class to generate a more informative error message for type issues, so we can use that here.

cpp11/inst/include/cpp11/r_vector.hpp

Lines 26 to 39 in 23ae34f

	class type_error : public std::exception {
	public:
	type_error(int expected, int actual) : expected_(expected), actual_(actual) {}
	virtual const char* what() const noexcept {
	snprintf(str_, 64, "Invalid input type, expected '%s' actual '%s'",
	Rf_type2char(expected_), Rf_type2char(actual_));
	return str_;
	}
	private:
	int expected_;
	int actual_;
	mutable char str_[64];
	};

[sbearrows]

Okay awesome thank you!

[sbearrows]

Okay I will make a new issue to change instances of cpp11::stop to C++ style exceptions.

[jimhester]

LGTM, feel free to merge it once you are ready.