Bignum divison and value assignment in c++

I'm writing my own bignum class for operating on large numbers. So far I've overloaded the operator= and operator+. How do I perform long division?

Also, right now I can only assign values within the range of integers to the bignum object. How do I assign values that fall outside the int range? Is it possible to do this without strings?

#include <iostream>

using namespace std;
class bignum
{
public:
    int number[20];
    bignum operator + (bignum);
    bignum operator = (int);
    void output()
};

bignum bignum::operator= (int j)
{
    int f;
    f=j;
    for(int k=0; k<=19; k++)
    {
       number[k]=0;
    }
    for(int l=19; l>=0,f>0; l--)
    {
       number[l]=(f%10);
       f/=10;
    }
}

bignu开发者_高级运维m bignum::operator+ (bignum b) 
{
    bignum a;
    int carry=0;
    for(int k=0; k<=19; k++)
    {
        a.number[k]=0;
    }
    for(int i=19; i>=0; i--)
    {
        a.number[i]= number[i]+b.number[i]+a.number[i];
        if(a.number[i]>9)
        {
        carry=(a.number[i]/10);
        a.number[i-1]+=carry;
        a.number[i]=(a.number[i]%10);
        }
    }

    return a;
}

int main()
{
    bignum a,b,c;
    a=9999;
    b=a+a;
    //for(int k=1; k<=9; k++)
    //b.number[k]=0;
    //b=a+a;
    for(int k=0; k<=19; k++)
    cout<<b.number[k];
    cin.get();
}

---

For assigning big numbers the usual way is strings. This usually only happens at the interface to your calculations and so is not a problem. Another way would be to have a template constructor that takes a range of chars that you interpret as a Two's Compliment number (I prefer this method, but I havent seen it used very often).

If you are serious about implementing a BigNum class then I would suggest that you read up about Expression Templates as a way to reduce the cost of temporaries in natural looking code.