ios:app doesn't work.

Question

Hi! I've made a simple calculator which saves history of calculations in history.txt. I wanted to use ios:app to not overwrite data. The problem is ios:app is detected as bug. Thanks!
Code:
#include <iostream>
#include <windows.h>
#include <conio.h>
#include <ostream>
#include <fstream>

using namespace std;

int main()
{
int operation, x, y, result;
string answer;

restart:

cout << "\nChoose operation" << endl;
cout << "[1] Addition\n[2] Subtraction\n[3] Multiplication\n[4] Division\n"<<endl;

cin>>operation;

cout << "Input first number: " <<endl;
if (!(cin>>x)){
cerr << "It's not number!";
exit(0);
}

cout << "Input second number: " <<endl;
if (!(cin>>y)){
cerr << "It's not number!";
exit(0);
}

switch(operation)
{
case 1:
result=x+y;
break;

case 2:
result=x-y;
break;

case 3:
result=x*y;
break;

case 4:
result=x/y;
break;

default:
cout << "There is no such operation" <<endl;
exit(0);
}

/* Save data in history.txt */

fstream file;
file.open("history.txt" , ios::out | ios:app);

switch(operation)
{
case 1:
file<<"x+y="<<result<<endl;
break;

case 2:
file<<"x-y="<<result<<endl;
break;

case 3:
file<<"x*y="<<result<<endl;
break;

case 4:
file<<"x/y="<<result<<endl;
break;
}
file.close();

cout << "Result is " << result << "\n\n" <<endl;
Sleep(1000);

cout << "Do you want to leave? y/n" <<endl;
cin >> answer;

if(answer=="y"){
return 0;
}
if (answer=="n"){
goto restart;
}

cout << "Click any button to leave." <<endl;
getch();
return 0;
}

Answer 1

You used an incorrect flag. Instead of 'ios:app', the flag is 'ios::app'.

Also, calling <ostream>here is not required, since you call <iostream>.

Answer 2

Some headers you've included are Windows-specific and doesn't work in Code Playground (e.g. window.h, conio.h).

⬇ Related
https://www.sololearn.com/Discuss/691848/?ref=app

Answer 3

Thanks for answer! How simple it was.