C++: to_chars/from_chars

개요

• to_chars
  • 정수 혹은 부동 소수점 값을 문자 시퀀스로 변환
• from_chars
  • 문자 시퀀스를 정수 또는 부동 소수점 값으로 변환

예제

• 코드

    #include <array>
    #include <charconv>
    #include <iomanip>
    #include <iostream>
    #include <string>
    #include <string_view>

    using namespace std;

    void to_chars_test(auto... format) {
    	array<char, 10> a;

    	auto result = to_chars(a.data(), a.data() + a.size(), format...);
    	if (result.ec == errc()) {
    		cout << string_view(a.data(), result.ptr - a.data()) << endl;
    	} else {
    		cout << make_error_code(result.ec).message() << endl;
    	}
    }

    void from_chars_test(string s, auto type, auto... format) {
    	decltype(type) result = 0;

    	auto [ptr,
    		  ec]{from_chars(s.data(), s.data() + s.size(), result, format...)};
    	if (ec == errc()) {
    		cout << "result : (" << result << "), ptr : (" << ptr << ")" << endl;
    	} else {
    		cout << make_error_code(ec).message() << endl;
    	}
    }

    int main() {
    	to_chars_test(10);
    	to_chars_test(10, 16);
    	to_chars_test(+11);
    	to_chars_test(-11);
    	to_chars_test(3.14);
    	to_chars_test(3.14, chars_format::fixed);
    	to_chars_test(-3.14);
    	to_chars_test(-3.14, chars_format::scientific);
    	to_chars_test(12345678900);

    	cout << "------" << endl;

    	from_chars_test("10", int());
    	from_chars_test("+10", int());
    	from_chars_test("-10", int());
    	from_chars_test("AB", int(), 16);
    	from_chars_test("11 abc", int());
    	from_chars_test("3.14", int());
    	from_chars_test("3.14", double());
    	from_chars_test("12345678900", int());

    	return 0;
    }

• 실행 결과

    10
    a
    11
    -11
    3.14
    3.14
    -3.14
    -3.14e+00
    Value too large for defined data type
    ------
    result : (10), ptr : ()
    Invalid argument
    result : (-10), ptr : ()
    result : (171), ptr : ()
    result : (11), ptr : ( abc)
    result : (3), ptr : (.14)
    result : (3.14), ptr : ()
    Numerical result out of range