Question

UPDATE :

This question is not homework. And not waterproof apparantly…
I wanted a discussion about internal representation.
Of course : the add1000 ought to add 1000.

**Please answer in the spirit of this question… Making this waterproof would make this question longer without no reason.. **
You can beat a pure decimal representation
Changing internal representation in runtime
UPDATE 2 : see

Create a type that implements this interface :

interface INumber
    {
        void add1000();
        void SetValue(decimal d);
        decimal GetValue();         
    }

so that i iterates as fast as possible from 0 to 10 billion (american billion, so till 10e9) in this for loop :

private static void DoSomeAdding(INumber n)
        {
            Debug.Assert(n.GetValue()==0);

            for (long i=0; i<10000000000; i += 1000)
            {
                n.add1000();
            }

            Debug.Assert(n.GetValue() == 10000000000);

        }

So you can call it as :

DoSomeAdding(new YourNumberClass());

Answer 1

Like Anton’s solution, but with a bit more care 🙂 Oh, and I’ve changed the names to be more .NET-like.

public Number : INumber
{
    private decimal value = 0m;
    private int thousands = 0;

    public void Add1000()
    {
        thousands++;
    }

    void SetValue(decimal d)
    {
        value = d;
        thousands = 0;
    }

    decimal GetValue()
    {
        // Careful of the overflow... (do multiplication in decimal)
        value += thousands * 1000m;
        thousands = 0;
        return value;
    }
}