[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