functions

[koutsos1]

Hi,
So I have an assignment to do and it goes as follows.

Write a simple program which reads in 2 integers, a & b, from cin.
print out the values they entered, a & b
Pass a & b *by reference* to a function which will *swap* their values
Return back to main() and print out a & b again, showing that their values have been swaped.

and this is what I have so far...

#include <iostream>
using namespace std;

void duplicate (int& x, int& y)
{
x*=b/a;
y*=a/b;
}

int main ()
{
int a, b;
cout << "Enter first number:";
cin >> a;
cout << "Enter second number:";
cin >> b;
cout << "a = " << a << endl;
cout << "b = " << b << endl;
duplicate (a, b);
cout << "a= " << a << "', b= " << b;
return 0;
}

Any help or advice would be great.

Thanks

[Athar]

I don't think you got the meaning of swapping...
it means that after the call b should have the value of a and vice versa.


a and b aren't declared in duplicate.

[filipe]

First, you should give your functions meaningful names, not misleading ones. Here's how you could write that function:

void swap_values(int& x, int& y)
{
	int temp = x;
	x = y;
	y = temp;
}

You should notice a few things you were getting wrong. A reference acts exactly like the original object. There's no need to dereference it (and, to dereference a pointer, you say *ptr, not ptr*). Also, a function has no way of knowing about non-local, non-global variables (I'm ignoring class members for now).

Finally, what were you thinking by assigning some variable to b/a or a/b? That's certainly not swapping!

[koutsos1]

Yeah, I was confused, I was figuring that using a division of the numbers would swap their values, hence the a/b b/a stuff. And thank you guys for the help. Here is what I have now,

#include <iostream>
using namespace std;

void swap_values (int& x, int& y)
{
int temp = x;
x = y;
y = temp;
}

int main ()
{
int x, y;
cout << "Enter first number: ";
cin >> x;
cout << "Enter second number: ";
cin >> y;
cout << "x = " << x << endl;
cout << "y = " << y << endl;
return 0;
}

Im still a little confused as to how the the swapped values get printed

[Zhuge]

Well, um, they aren't, as you don't ever swap them in that code, and don't ever print them after the swap. Unless I'm misunderstanding you somewhere.

[koutsos1]

The assignment states:
Write a simple program which reads in 2 integers, a & b, from cin.
print out the values they entered, a & b
Pass a & b *by reference* to a function which will *swap* their values
Return back to main() and print out a & b again, showing that their values have been swapped.

So im confused on the last step

[filipe]

Pass a & b *by reference* to a function which will *swap* their values

You're missing this step. And you don't need to rename a and b to x and y. Those names are local to swap_values().

[binarybob350]

Need to call the swap_values function and print out x and y again.

int main ()
{
  int x, y;
  cout << "Enter first number: ";
  cin >> x;
  cout << "Enter second number: ";
  cin >> y;
  cout << "x = " << x << endl;
  cout << "y = " << y << endl;

  // ADD THE FOLLOWING 3 LINES
  swap_values( x, y );  
  cout << "x = " << x << endl;
  cout << "y = " << y << endl;

  return 0;
}