CODEWITHSUNDEEP
c++pointersoperatorschar
mathewM
mathewM

Reputation: 139

How to sum and subtract char* numbers?

My problem is that I don't know how to sum huge numbers (like "172839023498234792834798237494" or "-172839023498234792834798237494"). So I made char* m_value where I will store this kind of objects. Now what I want to do is making some basic arithmetic operations. Should I first convert it or use some like itoa ? In my case there is no other options then char* to store numbers.

Main.cpp

int main(int argc, char *argv[])
{
    LargeNumber l1;
    LargeNumber l3("172839023498234792834798237494"); 
    LargeNumber l7("-172839023498234792834798237494"); 

    l1 = l3 + l7;  //How to do it ?

    return 0;
}

LargeNumber.h

class LargeNumber{

      public:
      LargeNumber(char* value):m_value(value)
      {}

      LargeNumber operator+(const LargeNumber&);
      private:
      char* m_value;
}

LargeNumber.cpp

LargeNumber LargeNumber ::operator+(const LargeNumber &b)
{
        return LargeNumber ( ... );  //Sum both LargeNumber ???
}

Upvotes: 1

Views: 528

Answers (3)

tzerb
tzerb

Reputation: 1433

Instead of using a string, I'd do it as an array of int (or long). The algorithms for the operators would be just about what you'd do by hand.

Upvotes: 1

sbabbi
sbabbi

Reputation: 11181

Don't reinvent the whell, you should use a BigInteger library.

And anyway, C strings are not the best way to do that.

Upvotes: 3

Mahmoud Al-Qudsi
Mahmoud Al-Qudsi

Reputation: 29529

You will need to use a large numbers arithmetic library. GMP is a good option. Your processor cannot natively perform operations on numbers of this size, so these libraries take care of all the old-school math for you in software.

Upvotes: 4

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