C++, If...Else with strings and special characters - c++

Question

I was trying to create a simple program to help my students to train German irregular verbs, but I have had problems with special characters and If statement. Basically it does not recognise the ä ö ü and ß, and output is therefore the Else statement (¨Nicht Gut"). How could I fix it?
#include <iostream>
#include <conio.h>
#include <locale.h>
using namespace std;
int main () {
setlocale(LC_CTYPE, "German");
string Antwort1;
string Antwort2;
string Antwort3;
getline(cin, str);
cout << str;
cout << "Präsens von BEHALTEN (du)" << endl;
cin >> Antwort1;
if (Antwort1 == "behältst") {
cout << "Gut!" << endl;
}
else {
cout << "Nicht Gut" << endl;
}
cout << "Präsens von BEHALTEN (er/sie/es/man) " << endl;
cin >> Antwort1;
if (Antwort1 == "behält") {
cout << "Gut!" << endl;
}
else {
cout << "Nicht Gut" << endl;
}
return 0;
}
I tried with
if (Antwort1 == (LC_CTYPE, "German"),"behält")
but then it causes the contrary effect. Then every single string I write is valid ("Gut").

Answer 1

My answer applies to the Windows 10 console using the classic default Command Prompt (I haven't tried it with other systems like PowerShell, nor I have tried these experiments on Linux yet).
It seems to me that, as of today (23 February 2022), Windows 10's Command Prompt and the Microsoft C/C++ Runtime of VS2019 don't support Unicode UTF-8 well: See, for example, this blog post showing a CRT crash you get when trying to call:
_setmode(_fileno(stdout), _O_U8TEXT);
and printing UTF-8 text using std::cout.
In my experience, you can make Unicode work in Windows Command Prompt using Unicode UTF-16. You can still use UTF-8 in your C++ application, but you have to convert between UTF-8 and UTF-16 at the Windows boundaries.
I modified your code to use Unicode UTF-16, and the code seems to work correctly when compiled with Visual Studio 2019, and executed inside the Windows Command Prompt:
// Used for _setmode calls
#include <fcntl.h>
#include <io.h>
#include <stdio.h>
// Console I/O with Unicode UTF-16 wcin, wcout and wstring
#include <iostream>
#include <string>
using std::wcin;
using std::wcout;
using std::wstring;
int main() {
// Enable Unicode UTF-16 console input/output
_setmode(_fileno(stdout), _O_U16TEXT);
_setmode(_fileno(stdin), _O_U16TEXT);
wcout << L"Präsens von BEHALTEN (du) \n";
wstring Antwort1;
wcin >> Antwort1;
if (Antwort1 == L"behältst") {
wcout << L"Gut! \n";
} else {
wcout << L"Nicht Gut \n";
}
}
Note the use of L"..." to represent UTF-16 string literals, and the use of wchar_t-based std::wcout, std::wcin, and std::wstring instead of the char-based std::cout, std::cin and std::string.