Hugeint Class Problem

Hello,

As given in book of Deitel and Deitel, i am trying to make a hugeint class which adds and subtracts a 40 digit number. I have successfully done the add member function but i want help from members to make the subtract function successful. I have done it and it works for some data sets but for some it doesn't. This is the code that i have worked so far

Code:

#include <iostream.h>
#include <string.h>
class hugeint
{
  int a[40];
  char s[40];
	public:
		hugeint(){}
		hugeint(char *);
		void operator+(hugeint);
		void operator-(hugeint);
		void putdata();
};
void hugeint::operator+(hugeint b)
{
 int i,l,carry=0;
 hugeint temp;
 if(strlen(s)>strlen(b.s))
	l=strlen(s);
 else
	l=strlen(b.s);
 for(i=39;i>=40-l;i--)
 {
   temp.a[i]=a[i]+b.a[i]+carry;
   carry=0;
   if(temp.a[i]>9)
   {
		carry++;
		a[i]=a[i]%10;
   }
 }
 if(a[i]>9)
 {
	a[i]=a[i]%10;
	a[i-1]=1;
	l++;
 }
 cout<<"\n\nThe Addition Is :\n";
 for(i=40-l;i<40;i++)
	cout<<temp.a[i];
}
void hugeint::operator-(hugeint b)
{
  int i,l,borrow;
  hugeint temp;

 if(strlen(s)>strlen(b.s))
	l=strlen(s);
 else
	l=strlen(b.s);
 for(i=39;i>=l;i--)
 {
	temp.a[i]=a[i]-borrow-b.a[i];
	borrow=0;
	if(temp.a[i]<0)
	{
		borrow++;
		temp.a[i]=a[i]+10-b.a[i];
	}
 }
 cout<<"\n\nThe Subtraction Is :\n";

  for(i=40-l;i<40;i++)
	cout<<temp.a[i];

}
void hugeint::putdata()
{
 int i;
 cout<<"\n\nThe Number Is :\n";
 for(i=40-strlen(s);i<40;i++)
	cout<<a[i];
}
hugeint::hugeint(char *t)
{
	strcpy(s,t);
	for(int i=0;i<40;i++)
		a[i]=0;
	int j;
	for(i=40-strlen(s),j=0;i<40;j++,i++)
		a[i]=s[j]-'0';
}


int main(void)
{
 hugeint a("871"),b("77");
 a.putdata();
 b.putdata();
 a-b;

 return 0;
}

I'd say the problem is here:

Code:

		temp.a[i]=a[i]+10-b.a[i];

That doesn't take 'borrow' into account. I think you should replace that line with just:

Code:

		temp.a[i] += 10;

Thanks Imalc works like a charm now!