pointer question

[sde]

total newb example, but i was wondering about pointers ..

please read the comments:

void swap(int *a1, int *a2)
{
  // is this next line right?
  // it seems like i should use *a1>*a2
  if(a1 > a2)
  {
    int temp;
    temp = *a1;
    *a1 = *a2;
    *a2 = temp;
  }
}

[Valmont]

Your comment is correct. Use *.
But you need to pass arguments like:

int a, b;
	a = 8;
	b = 5;
	swap(&a, &b);

You could do yourself a favor and implement this, wich is much neater:

void swap(int &a1, int &a2)
{
	if(a1 > a2)
	{
		int temp;
		temp = a1;
		a1 = a2;
		a2 = temp;
	}
}


int main(int argc, char* argv[])
{

	int a, b;
	a = 8;
	b = 5;
	swap(a, b);
	cout<<"a: "<<a<<" b: "<<b<<endl;
	return 0;
}

You could do yourself even another favor: not calling your functions "swap".
Why? Because swap is already defined in the namespace std;
Check this complete code out:

#include<iostream>

using namespace std;

int main(int argc, char* argv[])
{
	int a, b;
	a = 8;
	b = 5;
	swap(a, b);
	cout<<"a: "<<a<<" b: "<<b<<endl;
	return 0;
}

Better rename your functions to something everyone understands in the given situation in general.

[sde]

ok, thanks.

i just picked up a book i've had and was going through it and that line didn't make sense.

i just want to verify ... that line should be ..

if( *a1 > *a2 )

right?

[Amaranthine]

couldn't you use the assembly xchg instruction for that?

[joe_bruin]

i just want to verify ... that line should be ..

right.

void swap(int &a1, int &a2)

this doesn't work in c. you didn't specify whether you wanted c or c++. anyway, this is less flexible (since you actually can't use it for type "int *" variables, only type "int").

couldn't you use the assembly xchg instruction for that?

no.

[sde]

yes, it was a c++ example

so i passed 2 pointers into the function.

i compare the value of a1 to the value of a2 without the *

yet, when i assign a new value to a1, i need to use the * before it.

i guess not everything has to make sense. =)

thanks joe