Overloading the "abs" function

[Shane]

Well, to start off, I am attempting to do one of the programming projects in Problem Solving with C++ by Walter Savitch. The program asks me to overload the "abs" function using the "long", "int", "float", and "double" types, which, I try to do here:

 #include<iostream>
#include<cstdlib>
using namespace std;

int abs(int i); // Function Definitions
double abs(double d);
float abs(float f);
long abs(long l);

int main()
{
    int i = 1;
    double d = 2.0;
    float f = 3.0;
    long l = -4;
    cout << "Overloading Functions\n";
    cout << "Int: " << abs(i) << endl;
    cout << "Float: " << abs(d) << endl;
    cout << "Double: " << abs(f) << endl;
    cout << "Long: " << abs(l) << endl;
    
    system("PAUSE");
    return 0;
}

With the errors being as follows:

In function `int main()':
note :5 candidates are: int abs(int)
20 call of overloaded `abs(long int&)' is ambiguous
note double abs(double)
note float abs(float)
note long int abs(long int)
note long long int __gnu_cxx::abs(long long int)
note long int std::abs(long int)

Using latest beta of DevC++...not sure if I am doing something blatantly obvious as far as overloading goes, or maybe I just misunderstood the concept...but from the tutorials and information I have read...it looks right, but alas, I am not sure what's wrong. Any help would be greatly appreciated...my goal is to have a good understanding of c++.

[Dave_Sinkula]

Namespace issue? If you actually defined these functions but used this

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

instead of this

#include<iostream>
using namespace std;

would the problem persist?

[grumpy]

There are some functions in the std namespace named abs. You're probably clashing with them.

[Shane]

Namespace issue? If you actually defined these functions but used this
Code:
#include <iostream>
using std::cout;
using std::endl;instead of this
Code:
#include<iostream>
using namespace std;would the problem persist?

It turns out, that I had to do it this way. At first I was under the impression that I had to overload the predefined function "abs" to work with long, double, and float. But it turns out, I had to use my own written function of "abs" and overload it that way. Thanks for the replies, it helped me understand what my problem was.

[ILoveVectors]

#include<iostream>
#include<cstdlib>
using namespace std;

template <typename T>
T abs1(T i)
{
	return abs(i);
}

int main()
{
    int i = 1;
    double d = 2.0;
    float f = 3.0;
    long l = -4;
    cout << "Overloading Functions\n";
    cout << "Int: " << abs1(i) << endl;
    cout << "Float: " << abs1(d) << endl;
    cout << "Double: " << abs1(f) << endl;
    cout << "Long: " << abs1(l) << endl;
    
    system("PAUSE");
    return 0;
}

[Shane]

Hmmm, this is only chapter three of the book, talking about functions and function calls, templates aren't until later in the book, but still cool nonetheless.