There is no theoretical limit. The BigInteger class allocates as much memory as it needs for all the bits of data it is asked to hold. There are, however, some practical limits, dictated by the memory available. And there are further technical limits, although you’re very unlikely to be affected: some methods assume that the … Read more
As of .NET 4.0 you can use the System.Numerics.BigInteger class. See documentation here: http://msdn.microsoft.com/en-us/library/system.numerics.biginteger(v=vs.110).aspx Another alternative is the IntX class. IntX is an arbitrary precision integers library written in pure C# 2.0 with fast – O(N * log N) – multiplication/division algorithms implementation. It provides all the basic operations on integers like addition, multiplication, comparing, … Read more
BigInteger is capable of holding far bigger numbers than Long. BigInteger seems capable of holding (2 ^ 32) ^ Integer.MAX_VALUE, though that depends on the implementation (and, even if truly unbounded in the implementation, there will eventually be a physical resource limit) See explanation here. The range of Long is [-9,223,372,036,854,775,808, +9,223,372,036,854,775,807]. Long will perform … Read more
Use a loop: BigInteger randomNumber; do { randomNumber = new BigInteger(upperLimit.bitLength(), randomSource); } while (randomNumber.compareTo(upperLimit) >= 0); on average, this will require less than two iterations, and the selection will be uniform. Edit: If your RNG is expensive, you can limit the number of iterations the following way: int nlen = upperLimit.bitLength(); BigInteger nm1 = … Read more
I think a programmer should have implemented his own bignum-library once, so welcome here. (Of course, later you’ll get that BigInteger is better, and use this, but it is a valuable learning experience.) (You can follow the source code of this course life on github. Also, I remade this (a bit polished) into a 14-part … Read more
A fun challenge. 🙂 I assume that you want integers of arbitrary length. I suggest the following approach: Consider the binary nature of the datatype “int”. Think about using simple binary operations to emulate what the circuits in your CPU do when they add things. In case you are interested more in-depth, consider reading this … Read more
GMP is the popular choice. Squeak Smalltalk has a very nice library, but it’s written in Smalltalk. You asked for relevant books or articles. The tricky part of bignums is long division. I recommend Per Brinch Hansen’s paper Multiple-Length Division Revisited: A Tour of the Minefield.
Using the constructor BigInteger(String val) Translates the decimal String representation of a BigInteger into a BigInteger. Javadoc
The number is held in an int[] – the maximum size of an array is Integer.MAX_VALUE. So the maximum BigInteger probably is (2 ^ 32) ^ Integer.MAX_VALUE. Admittedly, this is implementation dependent, not part of the specification. In Java 8, some information was added to the BigInteger javadoc, giving a minimum supported range and the … Read more
You can use the BigInteger class for integers and BigDecimal for numbers with decimal digits. Both classes are defined in java.math package. Example: BigInteger reallyBig = new BigInteger(“1234567890123456890”); BigInteger notSoBig = new BigInteger(“2743561234”); reallyBig = reallyBig.add(notSoBig);