fixing signed numbers multiplication

[MahmoudRizk]

There were a bug when multiplying signed numbers, so i fixed it. #26

[kasparsklavins]

Can you give an example of when it produces an incorrect result?

[MahmoudRizk]

#include <iostream>
#include"bigint.h"

using namespace std;
using namespace Dodecahedron;
int main(int argc, char* argv[]){

  Bigint a("-5");
  Bigint b("-10");
  Bigint c;
  c = a * b;
  cout << c<< endl;

  return 0;
}

output : - 50
correct : 50

#include <iostream>
#include"bigint.h"

using namespace std;
using namespace Dodecahedron;
int main(int argc, char* argv[]){

  Bigint a("5");
  Bigint b("-10");
  Bigint c;
  c = a*b;
  cout << c<< endl;

  return 0;
}

output : 50
correct : -50

#include <iostream>
#include"bigint.h"

using namespace std;
using namespace Dodecahedron;
int main(int argc, char* argv[]){

  Bigint a("-5");
  Bigint c;
  c = a * -5;
  cout << c<< endl;

  return 0;
}

output: - - 25
correct: 25

#include <iostream>
#include"bigint.h"

using namespace std;
using namespace Dodecahedron;
int main(int argc, char* argv[]){

  Bigint a("234523452356235423452345");
  Bigint c;
  c = a * -2;
  cout << c<< endl;

  return 0;
}

output : -469046-904712470-846904690
correct : -469046904712470846904690

[kasparsklavins]

Okay, thanks for the pull request.

I'll go over it this weekend.

[MahmoudRizk]

I recommend to check the Subtraction pull request #19 too, because i want to make sure that the division is working correctly since it depends on it.
@kasparsklavins

[kasparsklavins]

Sure.
Been busy lately but I'll get to it.