Asking for help on this exercise from DS Malik

[Bopaki]

a.Write the definition of the function setData of the class two.
b.Write the definition of the function print of the class two.

  #include<iostream>
using namespace std;

class one
{
public:
void print() const;
//Outputs the values of x and y
protected:
void setData(int u, int v);
//Postcondition: x = u; y = v;
private:
int x;
int y;
};
void one::setData(int u, int v)
{
     x = u;
     y = v;
}     
class two: public one
{
public:
void setData(int a, int b, int c);
//Postcondition: x = a; y = b; z = c;
void print() const;
//Outputs the values of x, y, and z
private:
int z;
};

void two::setData(int a, int b, int c)
{
     x = a : (u, v);
     y = b;
     z = c;
}
void yClass::two(int u, int v)
{
     a = u;
     b = v;
}
void two::print() const
{
     cout << a <<" "<< b <<" " << c <<endl;
}     

[Repeater]

Are you? Are you asking for help? If you were asking for help, there would be a question here.

[Bopaki]

I am getting these errors:

exercise9.cpp: In member function `void two::setData(int, int, int)':
C:\Dev-Cpp\exercise9.cpp:13: error: `int one::x' is private
C:\Dev-Cpp\exercise9.cpp:35: error: within this context
C:\Dev-Cpp\exercise9.cpp:13: error: `int one::x' is private
C:\Dev-Cpp\exercise9.cpp:35: error: within this context
C:\Dev-Cpp\exercise9.cpp:35: error: expected `;' before ':' token
C:\Dev-Cpp\exercise9.cpp:14: error: `int one::y' is private
C:\Dev-Cpp\exercise9.cpp:36: error: within this context
C:\Dev-Cpp\exercise9.cpp:14: error: `int one::y' is private
C:\Dev-Cpp\exercise9.cpp:36: error: within this context

Execution terminated

[MikeyBoy]

The error message is self-explanatory. one::x is private, as defined on line 13. You can't access it it directly from two.

Also, this is an identical problem to the one you asked about in http://www.cplusplus.com/forum/beginner/265687/ .

[Enoizat]

I am getting these errors:
`int one::x' is private within this context

If you declare ‘something’ private inside a class/struct, that ‘thing’ cannot be accessed from outside the class.
Derived classes don’t make any exception.

class MyBase {
public:
private:
    int base_x = 2;
};


class MyDerived : public MyBase {
public:
private:
    int derived_x = base_x; // I can't! “base_x” is a private member of MyBase
};

To access those members, you can use the ‘usual’ getter/setter methods:

class MyBase {
public:
    int getBaseX() const
    {
        return base_x;
    }

private:
    int base_x = 2;
};


class MyDerived : public MyBase {
public:
private:
    int derived_x = getBaseX(); // Ok, “gatBaseX” is public
};

- - -

I am getting these errors:
expected `;' before ':' token

This line of code is wrong:
x = a : (u, v);

1) ‘x’ a private member of ‘one’;
2) ‘a’ cannot be assigned by parenthesis inside two::setData() — do use assignment operator ‘=’.
Please note you can use member initializer lists only with class constructors
https://en.cppreference.com/w/cpp/language/initializer_list
3) there’s an extra colon ‘:’, probably left by some copy&paste operation.


- - -
Apart from those, there are other issues.

1) void yClass::two(int u, int v)
The class name is ‘two’. Did you meant
void two::yClass(int u, int v) ?
Otherwise you are defining a ‘two(int, int)’ method of an unknown class ‘yClass’.


2) A comment in class ‘two’ says: //Postcondition: x = a; y = b; z = c;
If it is correct, it means this exercise is setting a trap for you.
You need to inizialize the base class (=‘one’) properties ‘x’ and ‘y’ from the arguments passed to the derived class ‘two’ setData() method.

Hint: remember there also is a one::setData() method…


- - -
One last thing, but please don’t take offense. It seems you’re getting worse at indenting your code.
Please consider for who reads (i.e. for us), a well indented code is far easier to understand.
Isn’t it?

#include <iostream>


class one
{
public:
    void print() const;
    //Outputs the values of x and y

protected:
    void setData(int u, int v);
    //Postcondition: x = u; y = v;

private:
    int x;
    int y;
};


void one::setData(int u, int v)
{
    x = u;
    y = v;
}


class two: public one
{
public:
    void setData(int a, int b, int c);
    //Postcondition: x = a; y = b; z = c;
    void print() const;
    //Outputs the values of x, y, and z

private:
    int z;
};


void two::setData(int a, int b, int c)
{
    x = a : (u, v);
    y = b;
    z = c;
}


void yClass::two(int u, int v)
{
    a = u;
    b = v;
}


void two::print() const
{
    std::cout << a << ' ' << b << ' ' << c << '\n';
}

[Bopaki]

Thank you all!!!
This function sorted out my problem eventually

void two::setData(int a, int b, int c)
{
    setData(a, b, c);
}