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
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
The GNU Multiple Precision Arithmetic Library does what you want http://gmplib.org/ Gnu MP is a C library but it has a C++ class Interface and if you are interested only in big integers, you may just deal with mpz_class. Look at the sample below which I took from the page C++ Interface General int main … 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
It sounds like you’re looking for a way to enter Arbitrary Precision numbers. here are two libraries you could use: GMP and MAPM
It’s all a matter of adequate storage and algorithms to treat numbers as smaller parts. Let’s assume you have a compiler in which an int can only be 0 through 99 and you want to handle numbers up to 999999 (we’ll only worry about positive numbers here to keep it simple). You do that by … Read more
While looking for an big integer library for an ElGamal crypto implementation I tested several libraries with the following results: I recommend this one: Tom Wu’s jsbn.js (http://www-cs-students.stanford.edu/~tjw/jsbn/) Comprehensive set of functions and fast Leemon Baird’s big integer library (http://www.leemon.com/crypto/BigInt.js) Comprehensive set of functions and pretty fast BUT: Negative number representation is buggy! bignumber.js (https://github.com/MikeMcl/bignumber.js) … 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
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);
For those with a maths background it is a surprising feature that System.out.println(“=” + (-3 % 4)); for example, returns -3 instead of 1 (which would be in the range [0,3]); Edit: in other words, the error message error message: Exception in thread “main” java.lang.ArrayIndexOutOfBoundsException: -8 is ultimately caused by (n % m) can return … Read more