Switch statement

I'm having problems with my switch statement, i try to call a member function of my calculator class inside of my switch statement and i keep getting errors.

Code:

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main.cpp    18  error: expected primary-expression before "double"

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I have 5 of the same errors, here is the switch statement:

Code:

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switch (choice)
{
    case '1':
    NewCalc.Multiply(double, double);
    break;
    case '2':
    NewCalc.Multiply(double, double, double);
    break;
}

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Obviously it's not finished yet but i don't want to carry on if it's got errors.
Can someone help me out?

Perhaps you have forgotten that double is a keyword used to declare double precision floating point variables? ;)

Ok, but when i get rid of the doubles it keeps saying that the function cannot be overloaded.

What did you try in getting rid of the doubles? It looks like all you are trying to do is call one of two functions depending on the case block entered.

Yup, that's it, but i can't get it to work, obviously, i have no idea why my compiler won't let me use keywords in switch statements.

This is confusing me a bit now:confused:

Quote:

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Yup, that's it, but i can't get it to work, obviously, i have no idea why my compiler won't let me use keywords in switch statements.

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Are you trying to define the functions? It is simply invalid syntax. To call a function that takes arguments, you have to pass something, be it a literal, a temporary or a variable.

I have declared and defined my functions in other files, i am simply trying to use my function :p

In that case, I would expect to see something like:

Code:

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double num = 1.2;
switch (choice)
{
    case '1':
    NewCalc.Multiply(3.4, 5.6);
    break;
    case '2':
    NewCalc.Multiply(num, num, num);
    break;
}

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I tried that, but i get the error:

Code:

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Num1 undefined (first use this function)

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It is really anoying!!!

Oh yeah... An the numbers are what the user imputs.

Now it looks like you are using a variable before defining it.

Hate to say this, but this kind of newbie problems seem rather uncharacteristic of you... perhaps you should get some rest?

And/or post the latest code, including the surrounding context.

Ok, i think i get what i've done wrong here, but i'll fix it tomorrow, my mam is just about to steel my computer for the next hour or so, and i'm tired, i've been working on this project all night, i don't know how proffesional programmers do this stuff 24/7.

Quote:

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Originally Posted by laserlight

Hate to say this, but this kind of newbie problems seem rather uncharacteristic of you... perhaps you should get some rest?

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Thanks, i'll take that as a compliment;)

Quote:

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Originally Posted by beene

i don't know how proffesional programmers do this stuff 24/7.

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two words, COFFEE and DELIVERY ;)

Hi everyone, i have just came home and fixed it, it was easy.
Thanks for all of your help though, i really appreciate it, it was such a nooby problem, i probably was to tired yesterday, anyway, here is the code, all i have to do is add a do while loop and there you have it, my OOP Calculator...

main.cpp

Code:

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#include <iostream>
#include "Functions.h"

int main()
{
    int choice;
    double _Num1;
    double _Num2;
    double _Num3;
    std::cout << "Welcome to my prototype Calculator with the basic functions" << std::endl;
    std::cout << "of Addition, Subtraction, Multiplication and Division" << std::endl;
    std::cout << "\nThis Calculator has the ability to Add, Subtract, Multiply" << std::endl;
    std::cout << "and Divide 3 numbers as well as two" << std::endl;
    std::cout <<"\nWhat would you like to do?" << std::endl;
    calculator NewCalc;
    NewCalc.Menu();
    std::cin >> choice;
    switch (choice)
    {
        case 1:
        NewCalc.Multiply(_Num1, _Num2);
        break;
        case 2:
        NewCalc.Multiply(_Num1, _Num2, _Num3);
        break;
        case 3:
        NewCalc.Divide(_Num1, _Num2);
        break;
        case 4:
        NewCalc.Divide(_Num1, _Num2, _Num3);
        break;
        case 5:
        NewCalc.Add(_Num1, _Num2);
        break;
        case 6:
        NewCalc.Add(_Num1, _Num2, _Num3);
        break;
        case 7:
        NewCalc.Subtract(_Num1, _Num2);
        break;
        case 8:
        NewCalc.Subtract(_Num1, _Num2, _Num3);
        break;
    }
    return 0;
}

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Funtions.cpp

Code:

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#include <iostream>
#include "Functions.h"

calculator::calculator()
{
    result = new double;
    _Num1 = Num1;
    _Num2 = Num2;
    _Num3 = Num3;
}

calculator::~calculator()
{
    delete result;
}

void calculator::Menu()
{
    std::cout << "Multiply 2 numbers (1)" << std::endl;
    std::cout << "Multiply 3 numbers (2)" << std::endl;
    std::cout << "Divide 2 numbers  (3)" << std::endl;
    std::cout << "Divide 3 numbers  (4)" << std::endl;
    std::cout << "Add 2 numbers      (5)" << std::endl;
    std::cout << "Add 3 numbers      (6)" << std::endl;
    std::cout << "Subtract 2 numbers (7)" << std::endl;
    std::cout << "Subtract 3 numbers (8)" << std::endl;
}

double calculator::Add(double Num1, double Num2)
{
    std::cout << "Type in the 2 numbers that you wanted to Add together..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    *result = Num1 + Num2;
    std::cout << "\nResult: " << *result << std::endl;
}

double calculator::Add(double Num1, double Num2, double Num3)
{
    std::cout << "Type in the 3 numbers that you want to Add together..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    std::cout << "\n...And now the last" << std::endl;
    std::cin >> Num3;
    std::cin.ignore();
    *result = Num1 + Num2 + Num3;
    std::cout << "\nResult: " << *result << std::endl;
}

double calculator::Subtract(double Num1, double Num2)
{
    std::cout << "Type in the 2 numbers that you want to Subtract from eachother..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    *result = Num1 - Num2;
    std::cout << "\nResult: " << *result << std::endl;
}

double calculator::Subtract(double Num1, double Num2, double Num3)
{
    std::cout << "Type in the 3 numbers that you want to Subtract from eachother..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    std::cout << "\n...And now the last" << std::endl;
    std::cin >> Num3;
    std::cin.ignore();
    *result = Num1 - Num2 - Num3;
    std::cout << "\nResult: " << *result << std::endl;
}

double calculator::Multiply(double Num1, double Num2)
{
    std::cout << "Type in the 2 numbers that you want to Multiply together..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    *result = Num1 * Num2;
    std::cout << "\nResult: " << *result << std::endl;
}

double calculator::Multiply(double Num1, double Num2, double Num3)
{
    std::cout << "Type in the 3 numbers that you want to Multiply together..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    std::cout << "\n...And now the last" << std::endl;
    std::cin >> Num3;
    std::cin.ignore();
    *result = Num1 * Num2 * Num3;
    std::cout << "\nResult: " << *result << std::endl;
}

double calculator::Divide(double Num1, double Num2)
{
    std::cout << "Type in the 2 numbers that you want to Divide..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    *result = Num1 / Num2;
    std::cout << "\nResult: " << *result << std::endl;
}

double calculator::Divide(double Num1, double Num2, double Num3)
{
    std::cout << "Type in the 3 numbers that you want to Divide..." << std::endl;
    std::cin >> Num1;
    std::cin.ignore();
    std::cout << "\n...And now the next" << std::endl;
    std::cin >> Num2;
    std::cin.ignore();
    std::cout << "\n...And now the last" << std::endl;
    std::cin >> Num3;
    std::cin.ignore();
    *result = Num1 / Num2 / Num3;
    std::cout << "\nResult: " << *result << std::endl;
}

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Funtions.h

Code:

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class calculator
{
    public:
    calculator();
    ~calculator();

    void Menu();

    double Multiply(double Num1, double Num2);
    double Multiply(double Num1, double Num2, double Num3);

    double Divide(double Num1, double Num2);
    double Divide(double Num1, double Num2, double Num3);

    double Add(double Num1, double Num2);
    double Add(double Num1, double Num2, double Num3);

    double Subtract(double Num1, double Num2);
    double Subtract(double Num1, double Num2, double Num3);

    protected:
    double _Num1;
    double _Num2;
    double _Num3;
    double Num1;
    double Num2;
    double Num3;
    double *result;
};

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Critisicm welcome, i rushed through this so if i could make it better i would appreciate that help also, and thanks again.

Code:

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calculator::calculator()
{
    result = new double;
    _Num1 = Num1;
    _Num2 = Num2;
    _Num3 = Num3;
}

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and why exactly do you need declare reslut as pointer to double and allocate it dynamically?

and why do you initialize _NumX with not initialized vaiables NumX?

Quote:

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Originally Posted by vart

and why exactly do you need declare reslut as pointer to double and allocate it dynamically?

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I suppose i don't need to, just a spur-of-the-moment kind of thing.

I noticed a rather unfortunate choice of variable names:

Code:

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double _Num1;
double _Num2;
double _Num3;

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The C++ Standard states that "each name that contains a double underscore (_ _) or begins with an underscore followed by an uppercase
letter is reserved to the implementation for any use". As such, you should use a different variable naming convention. It seems to me that something as straightforward as num1, num2 and num3 will do.

It also seems that these three variables were not really used at all. Likewise, it looks like much of your class actually functions as a namespace with the member variables left largely unused except for result. After all, although you use Num1 and Num2 in various member functions, you have parameters of the same name, thus those parameters are used and the member variable names are hidden.

I have went over my code and realised that it was a bit of a mess, thanks to the people on this bored for helping me realise this, so I have reformatted(I think that's the correct word) my code and come across a few errors, I have moved....

Code:

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double num1;
double num2;
double num3;
double Num1;
double Num2;
double Num3;

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....to the constructor and removed the other declarations from the program, but I don't see why i get these errors:

Code:

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main.cpp          28    error: 'num1' undeclared(first use this function)

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I thought that whenever an object is made that the constructor is called. So why are my variables not declared?

Am I missing something here?

I believe variables declared inside a constructor are local to that constructor, just like a regular function. You need variables that have class-wide scope to access them anywhere inside the class.

Right, is there another way to tidy up my code without making the variables global?

Yes: declare local and member variables as needed and keep them and their scopes straight.

Thanks a bunch.