Factorial

[Zexd]

I wrote a factorial function and it is working perfect :)
But only for the numbers until 65. I want it to be able to calculate even bigger numbers (like 100 or 1000). I maximized the size of value that the function is returning... Any ideas? Maybe storing it in array (tho I got no idea how :/ )

  #include <iostream>
#include <conio.h>

using namespace std;

unsigned long long int Factorial(int x);

int main()
{
    int a;
    cout << "Input a number! ._.\n";
    cin >> a;
    cout << Factorial(a) << "\n";
    getch();
    return 0;
}

unsigned long long int Factorial(int x)
{
     if(x > 1) return x * Factorial(x - 1);
     else return x;
}

And three additional questions...

What two pointers pointing at each other can do?
Can I make a pointer pointing at itself (if yes, what can it do?)?
And keywords private, explicit, friend (I understand classes).

Thank you! :) \n

[Smac89]

your factorial function does not have a default return value. One of your return statements cannot depend on a condition, so choose one of them and use that as the default return value.

int w = 2;
int *ptr1 = &w//2
int *ptr2 = ptr1;//2
ptr1 = ptr2;//2 

[Zexd]

Er... How does that answer my question?

My code is correct, I am sure in that :)
I just want an answer for bigger numbers, much bigger.

[Smac89]

If you want larger values, you might want to look into getting a biginteger library.

See the second code in this link:
http://www.cplusplus.com/forum/general/93643/#msg502709

[Zexd]

I don't want to use any libraries beside iostream, fstream and conio.h (maybe algorithm and iomanip).

[Smac89]

Well if you want larger values, either write it in python or any scripting languages or wait until c++ has support for big integer types.

Or make one...I believe someone made a fully functioning one written in c++ a while ago on this forum. If only I can find it...

Found this also:
http://www.cplusplus.com/forum/general/95596/#msg513774

He took down the links, but you can pm him for it (be nice :) )

[Danny Toledo]

http://www.cplusplus.com/forum/lounge/32041/