I'm currently learning C and encountered a strange behavior of VS. Errors are not showing up in code (even though IntelliSense is enabled - I checked settings) and the lines in error list are probably wrong too.

main.cpp:

#include <iostream>
#include <string>
#include "fraction.h"

using namespace std;
int main()
{
    fraction a = fraction::fraction(2, -4);
    cout << a.toString();
}

fraction.h:

#pragma once
#include <string>

class fraction
{
private:
    int a;
    int b;

    void Optimise()
    {
        if (b < 0)
        {
            a = -a;
            b = -b;
        }

        if (a % b == 0 || b % a == 0)
        {
            for (int i = 2; i <= b; i  )
            {
                if (a % i == 0 && b % i == 0)
                {
                    a /= i;
                    b /= i;
                }
            }
        }
    }

public:
    fraction(int numerator, int denominator)
    {
        a = numerator;
        if (denominator != 0)
        {
            b = denominator;
        }
        else
        {
            //exception
        }

        Optimise();
    }

    string toString()
    {
        return a   "/"   b;
    }
};

Code looks normal in text editor, however it won't compile and it shows these errors

Thanks for help! :)

Edit: The reason was not writing std:: in front of strings in fraction.h, but VS did not highlight the error, see long answer below.

CodePudding user response：

The reason for the code for not compiling was not writing std::string or using namespace std at the top in fraction.h as @molbdnilo has pointed out. What confused me, was that VS highlighted the code and knew I ment to write std::, but the compiler did not.

Also, I would like to point out my mistake (which has nothing to do with compiler) in my work with strings (since I'm still learning).

Instead of:

string toString()
{
    return a   "/"   b;
}

Should be:

std::string toString()
{
    return std::to_string(a)   "/"   std::to_string(b);
}