How to implement big int in C++

Question

I\'d like to implement a big int class in C++ as a programming exercise—a class that can handle numbers bigger than a long int. I know that there are several open sou

Answer 1

There's a complete section on this: [The Art of Computer Programming, vol.2: Seminumerical Algorithms, section 4.3 Multiple Precision Arithmetic, pp. 265-318 (ed.3)]. You may find other interesting material in Chapter 4, Arithmetic.

If you really don't want to look at another implementation, have you considered what it is you are out to learn? There are innumerable mistakes to be made and uncovering those is instructive and also dangerous. There are also challenges in identifying important computational economies and having appropriate storage structures for avoiding serious performance problems.

A Challenge Question for you: How do you intend to test your implementation and how do you propose to demonstrate that it's arithmetic is correct?

You might want another implementation to test against (without looking at how it does it), but it will take more than that to be able to generalize without expecting an excrutiating level of testing. Don't forget to consider failure modes (out of memory problems, out of stack, running too long, etc.).

Have fun!