Objects getting me down...:(

Well. I'm almost ashamed to ask this question. But I'm stumped. I'm trying to remember OOP (haven't programmed in awhile), and I'm having some trouble.

Code:

---

#include <iostream.h>

class CSubtraction
{
  int s1, s2;
public:
  void Equalize(int,int);
  int Subtract(void) {return (x-y);}
};

void CSubtraction::Equalize(int x, int y)
{
  x = s1;
  y = s2;
}

int main()
{
  CSubtraction sub;
  sub.Equalize(4,3);
  cout << "Answer: " << sub.Subtract();
  return 0;
}

---

I know it's some tiny little thing I missed, like a semi-colon or something. Just incase you haven't caught on, it's just supposed to subtract 4 and 3.

The errors:
Line 8: 'x' undeclared
Line 8: 'y' undeclared

Thanks guys. :)

Code:

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int Subtract(void) {return (x-y);}

---

... x, y are not declared. I think you meant ...

Code:

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int Subtract(void) { return s1 - s2; }

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Also, use this instead of those old headers:

Code:

---

#include <iostream>
using namespace std;

---

Thanks. I knew it was something stupid.

Quote:

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Originally posted by Speedy5
Also, use this instead of those old headers:

Code:

---

#include <iostream>
using namespace std;

---

[/B]

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I've seen this before. Why should I use it? And some people tell me that it pollutes the namespace. Is that true?

You'll also need to change this:

Code:

---

void CSubtraction::Equalize(int x, int y)
{
  x = s1;
  y = s2;
}

---

To this:

Code:

---

void CSubtraction::Equalize(int x, int y)
{
  s1 = x;
  s2 = y;
}

---

Quote:

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Originally posted by KneeLess
I've seen this before. Why should I use it? And some people tell me that it pollutes the namespace. Is that true?

---

Code:

---

#include <iostream.h>

---

is essentially the same as

Code:

---

#include <iostream>
using namespace std;

---

The second form wraps the header into the 'std' namespace. To avoid "polluting" the namespace, you can import separate pieces with the 'using' directive:

Code:

---

#include <iostream>
using std::cout;
using std::endl;

---

Or, you can just tag 'std::' onto the front of the identifiers:

Code:

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#include <iostream>
....
  std::cout << "hello world" << std::endl;

---

Also, the header files that end in '.h' are deprecated. Standard conforming compilers are not required to provide them.