Question

I am writing a class which needs accurate division of the BigInteger class in C#.

Example:

BigInteger x = BigInteger.Parse("1000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
BigInteger y = BigInteger.Parse("2000000000000000000000000000000000000000000000000000000000000000000000000000000000000");

x /= y;

Console.WriteLine(x.ToString());

//Output = 0

The problem is that being an Integer, naturally it does not hold decimal values.
How can I overcome this to get the real result of 0.5 (given example).

P.S. The solution must be able to accurately divide any BigInteger, not just the example!

Answer 1

In the above example, the numbers are still small enough to be converted to double, so in this case you can say

double result = (double)x / (double)y;

If x and y are too huge for a double but still comparable, maybe this great trick is helpful:

double result = Math.Exp(BigInteger.Log(x) - BigInteger.Log(y));

But in general, when the BigInteger are huge, and their quotient is huge too, this is hard to do without importing a third-party library.