How do you cin parameters?

[stariz]

How do you create a function that takes user-defined parameters? For example, say I had a function:

int Example(int x, int y){

answer = x+y;

return answer;

}

I understand I can cout << Example (4,6); to add 4 to 6; however, how do I allow a user to define the parameters before the function is called, i.e., make their inputs the parameters of the function?

Is using a function that takes parameters defined by a user particularly useful in certain situations?

PS. I am not trying to build a calculator; I was just using the above code as an example.

Thanks.

[tabstop]

Point your arrows the other way. You will need variables to store them to, and then call the function with those variables.

(ETA: Or if you don't want variables in main, you can do the cin read in your function. But you'll still need variables to read into.)

[AndrewHunter]

You may want to take a look here. There is a lot of good information.

[stariz]

Thanks for the link to the resources! I will be sure to go through the information; however, I just wanted to follow up on what tabstop said to see if I understood. This is what I came up with:

#include <iostream>

using namespace std;

class Abc{

public:
    int Example(int x, int y){

    answer = x+y;

    return answer;
}

private:
    int answer;

};

int main()
{
    int a;
    int b;
    Abc equation;

    cin >> a;
    cin >> b;

    cout << equation.Example(a,b);

}

Am I able to eliminate "int a" and "int b" from main somehow? I mean it works fine, but is it bad practice to have them there?

Sorry for being noob

Thanks again.

[Elkvis]

Thanks for the link to the resources! I will be sure to go through the information; however, I just wanted to follow up on what tabstop said to see if I understood. This is what I came up with:

#include <iostream>

using namespace std;

class Abc{

public:
    int Example(int x, int y){

    answer = x+y;

    return answer;
}

private:
    int answer;

};

int main()
{
    int a;
    int b;
    Abc equation;

    cin >> a;
    cin >> b;

    cout << equation.Example(a,b);

}

Am I able to eliminate "int a" and "int b" from main somehow? I mean it works fine, but is it bad practice to have them there?

Sorry for being noob

Thanks again.

there's absolutely nothing wrong with having them there. in fact, it's where they belong in a program like yours. making them global (outside the scope of any class, namespace, or function) would be very bad. it is best to avoid global variables whenever possible. it is sometimes necessary to have them, but those situations are not nearly as common as the actual usage of global variables.

[tabstop]

Am I able to eliminate "int a" and "int b" from main somehow? I mean it works fine, but is it bad practice to have them there?

Sorry for being noob

Thanks again.

What I meant was more on the lines of:

int Example() {
    int x, y;
    cin >> x >> y;
    int answer = x + y;
    return answer;
}

int main() {
    cout << Example() << endl;
}

where the variables move to the function instead.

[King Mir]

No, that's worse. You should have a function do either IO or computation, not both.

[CornedBee]

However, the class Abc is total overkill.

You want this:

int Example(int x, int y){
  answer = x+y;
  return answer;
}

int main()
{
    int a;
    int b;
    cin >> a;
    cin >> b;

    cout << Example(a,b);
}

[stariz]

Thanks everyone for the help; it is more useful than you know.

However, the class Abc is total overkill.

Yah, I was just trying to create a simple example that I could apply to my current project.

I recently decided to take a second major in CS which will be in affect as of next semester (starting in 2 weeks) and couldn't wait to get started so I decided to learn C++ by creating a program that a friend could use for actuarial studies. I had originally just written it as a list of commands and although it worked quite well, I wanted to practice writing it properly. Although I suspect it's not a lot better, I have managed to make all the variables used in calculations private at least and all the calculations are organised into various classes in separate files. The only public variables are 5 strings that are used to navigate between the various menus with lists of equations.

I asked about the function that could take user defined parameters as I was trying to separate the calculation and the interaction with the user somehow. For example, most of my functions look something like this:

void CompoundFunctions::PresentValue(){

    cout << "Size of regular payment (R): ";

    cin >> R;

    cout << endl << endl;

    cout << "Number of payments (n): ";

    cin >> n;

    cout << endl << endl;

    cout << "Interest rate (i) per period: ";

    cin >> i;

    cout << endl << endl;

    PV = R*((1 - pow((1 + i), -n) ) / i);

    cout.setf(ios::fixed);

    cout << "PV of annuity = " << setprecision(2) << PV << endl << endl;

}

My main() is pretty much a bunch of if statements within if statements within a do/while loop that call various functions such as the above.

If anyones bored enough to take a look (or wants a laugh perhaps?), I would be happy to send the code to get your opinion on how to rewrite the program according to "proper" C++ OOP conventions.

Or what would be a good type of program to attempt that would help me to learn OOP rules?

Thanks again.

[CornedBee]

OOP is not necessarily the best way to tackle any given program. And as a rough guideline, prefer function-local variables over member variables, even private ones.