What is wrong with this?!

[corseting]

Its having some problems with "radius".... Im not too sure what I've missed! thank you




#include<iostream>
#include<conio.h>
#include<cmath>
using namespace std;

class Circle
{
int radius;
};

void main()
{

void printArea(Circle c);
void printDiameter(Circle c);
Circle aBigCircle, aLittleCircle;

aBigCircle.radius = 50;
aLittleCircle.radius = 4;
printArea(aBigCircle);
printDiameter(aBigCircle);
printArea(aLittleCircle);
printDiameter(aLittleCircle);
getch();
}

void printArea(Circle)
{
double area;
area = radius * radius * 3.14159;
cout<<"A circle with radius "<<radius<<" has an area of "<<area<<endl;
}
void printDiameter(Circle)
{
int diam;
diam = radius * 2;
cout<<"A circle with radius "<<radius<<" has a diameter of "<<diam<<endl;
}

[Disch]

Its having some problems with "radius"

What kind of problem?

Are you getting an error? If yes, what is the error and what line is it on?

Is it compiling OK but it's not behaving how you expect? If yes, tell us what you expect and tell us how it's behaving.


Posting a block of code and saying "it doesn't work" is a great way to get ignored. Give us details. Help us help you.

[corseting]

Sorry about that..... heres a little more info..

Basically the program should print the Area and Diameter of "Big circle" (radius =50) and "little circle" (radius = 4).

Based on the functions at the bottom of the code which convert the radius numbers into area and diameter.

These are the errors that occur when I build (the build fails everytime)

1>h:\lab41\lab44\lab44\lab44.cpp(20): error C2248: 'Circle::radius' : cannot access private member declared in class 'Circle'
1> h:\lab41\lab44\lab44\lab44.cpp(10) : see declaration of 'Circle::radius'
1> h:\lab41\lab44\lab44\lab44.cpp(9) : see declaration of 'Circle'
1>h:\lab41\lab44\lab44\lab44.cpp(21): error C2248: 'Circle::radius' : cannot access private member declared in class 'Circle'
1> h:\lab41\lab44\lab44\lab44.cpp(10) : see declaration of 'Circle::radius'
1> h:\lab41\lab44\lab44\lab44.cpp(9) : see declaration of 'Circle'
1>h:\lab41\lab44\lab44\lab44.cpp(32): error C2065: 'radius' : undeclared identifier
1>h:\lab41\lab44\lab44\lab44.cpp(32): error C2065: 'radius' : undeclared identifier
1>h:\lab41\lab44\lab44\lab44.cpp(33): error C2065: 'radius' : undeclared identifier
1>h:\lab41\lab44\lab44\lab44.cpp(38): error C2065: 'radius' : undeclared identifier
1>h:\lab41\lab44\lab44\lab44.cpp(39): error C2065: 'radius' : undeclared identifier



The "radius" word in the code is underlined in red throughout my code indicating an error... but Im not sure what I did wrong... its definitely undeclared somewhere but I think I just need an extra set of eyes haha

As well, I feel like I dont have a link of somekind between the Big circle and Little Circle to print a response... although I thought it was covered with the line:

Circle aBigCircle, aLittleCircle;

Any help would be appreciated! sorry for the lack of info at first I was just trying to get it on here as fast as possible lol

[Disch]

OK you have a few problems.

#1 is that radius is private, so only functions within Circle can access it. If you want to access it outside of Circle, you must make it public:

class Circle
{
public:  // make it public
    int radius;
};

#2 is that if you use 'radius' outside of Circle, you have to specify whose radius you want. Remember that every circle has a radius, so you can't just print 'radius' and expect it to print the right value -- you need to tell it which Circle's radius you want to print.

Example:

Circle aBigCircle, aLittleCircle;

aBigCircle.radius = 50;  // this is good, you're saying you want to modify aBigCircle's radius
aLittleCircle.radius = 4;  // also good.  Modifying aLittleCircle's radius

//...

void printDiameter(Circle)
{
  int diam;
  diam = radius * 2;  // This is bad.
  // Whose radius?  aBigCircle's?  aLittleCircle's?  Some other circle?
  //  The compiler can't guess, it needs you to tell it which circle
  //  you probably meant to use whatever circle is passed to this function
  //   (which also means you might want to name it, so you can use it) 

[corseting]

Ahhhh that makes perfect sense with the public/private!

As for the radius within the functions, I understand what you mean, but not sure how to get there.

The idea is to print both the big and little circle area and diameter... I thought if I just left it as "radius" that it would do both but that seems to be where Im going wrong...

What could I add or remove to make it work the way I was attempting?

I know if I do....

area= aLittleCircle.radius * aLittleCircle.radius * 3.14159.... that doesnt seem to work... plus I think I would have to do 2 seperate functions that way.....

Could I change the parameters of the function? like....

void printArea (aBigCircle, aLittleCircle)?

Thank you!

[Disch]

You're passing a circle to the funciton. Logically you'd want to use that circle's radius.

So give that circle a name so you can use it:

void printDiameter(Circle c) // the circle is now named 'c'
{
  int diam;
  diam = c.radius * 2;  // use Circle c's radius

  //...
}

// then when you call the function:

printDiameter(aBigCircle);  // aBigCircle will be used as 'c', so this will print
    // aBigCircle's diameter

printDiameter(aLittleCircle); // now aLittleCircle will be used as 'c'

// etc.