overloading operators in C++

hertz

Im trying to overload the +operator in C++, I know you need to have a class built first because one of the arguements must come from that.

Its to do with adding two HugeInts, numbers bigger than 30 digits, they re added using an array.

the class looks something like this but I don't know what its all about,

class HugeInt {
friend ostream &operator<<(ostream &, HugeInt &);
friend istream &operator>>(istream &, HugeInt &);
friend HugeInt add(const HugeInt&, const HugeInt&);
public:
HugeInt(long=0); // conversion/default constructor
HugeInt(const char*); // conversion constructor
HugeInt operator+(HugeInt &); // add another HugeInt
HugeInt operator+(int); // add an int
HugeInt operator+(const char*); //add an int in a char*
private:
short integer[30];
};

Any help or insights would be appreciated..

Hertz

Blitzkrieger

I don't understand the question

To overload a funtion it's simply a question of giving it different arguments. Eg :

int addInts(int a, int b);
int addInts(int a, int b, int c);

If you use the function call :

x = addInts(a, b, c) ;

It will automatically use the second function.


Oh - I see what you mean Never mind the above

I don't know how to do it but any good book on C++ will tell you how. I believe the book I saw it in was "An Introduction to Programming with C++".

Tbh it seems like a lot of trouble to go to. I'm such a lazy sod I'd just write a addHugeInts function/class.

CH

>Any help or insights would be appreciated..
looks like you got this from C++ How to program (Deitel & Deitel), where the chapter on overloading is done very well

HugeInt operator+(HugeInt &); 	// add another HugeInt 
HugeInt operator+(int); 	// add an int 
HugeInt operator+(const char*); //add an int in a char* 

Here you have 3 overloaded member functions prototypes, which are overloading the + operator.
You must write a function for each of these functions, an example for the second member function could be:

HugeInt HugeInt::operator+(int rightHandSide)
{ 
	return *this + HugeInt(rightHandSide); 
}

When you use: yourObject1 + SOMETHING in main, the compiler evaluates which member function to use depending on what the right operand (SOMETHING) is.

If the right operand is an object of class HugeInt, the first member function is called: HugeInt operator+(HugeInt &);

yourObject1 = yourObject2 + yourObject3;

If the right operand is an integer, the second member function is called: HugeInt operator+(int);

yourObject1 = yourObject1 + 5;

If the right operand is a series of characters, the third member function is called: HugeInt operator+(const char*);

yourObject1 = yourObject1 + "999";

all of the above additions, will add the right operand to the private array of short ints.

regards.

Baz_

Well I have only glanced through that book but as far as I know the hugeinrt class is an array of chars I think which means your solution for function 2 will not work, ie. you cant add an integer to an array of chars.

What you need to do for that one is seperate the numbers of the int and then add the units to the units add carryover to the tens of hugeint then add the tens to the tens add carryover to hundreds then add hundreds to hundreds etc, etc, etc.

I'm too lazy to do any code but its more rewarding to do it yourself anyway.

timeout

below is how I did it for concatinating strings but its easy to change it for integers. Check with a library for books on C++. They got some good examples in them.


#include <iostream>
#include <string.h>


class test {
char name[20];
public:
test(char tname[]) {strcpy(name,tname);}
test operator+(test t1);
test operator=(test t1);
void display();
};

test test::operator+(test t1)
{
test temp(" ");

strcat(name,t1.name);
strcpy(temp.name,name);


return(temp);
}

test test::operator=(test t1)
{
strcpy(name,t1.name);

return *this;
}

void test :: display()
{
cout<<name <<"\n";

return;
}
int main()
{
test a("test"),b(" Run"),c(" ");
char now;

a.display();
b.display();
c.display();

c = a + b;
c.display();

cout<<"\njust a test";
cin>>now;

return(0);
}


Hope it helps:)