draggor / node-bigint

Arithmetic on big integers using libgmp

bigint

Arbitrary precision integral arithmetic for node.js!

This library wraps around libgmp's integer functions to perform infinite-precision arithmetic.

example

simple.js

var bigint = require('bigint');

var b = bigint('782910138827292261791972728324982')
    .sub('182373273283402171237474774728373')
    .div(8)
;
console.log(b);

---

$ node simple.js
<BigInt 75067108192986261319312244199576>

perfect.js

Generate the perfect numbers:

// If 2**n-1 is prime, then (2**n-1) * 2**(n-1) is perfect.
var bigint = require('bigint');

for (var n = 0; n < 100; n++) {
    var p = bigint.pow(2, n).sub(1);
    if (p.probPrime(50)) {
        var perfect = p.mul(bigint.pow(2, n - 1));
        console.log(perfect.toString());
    }
}

---

6
28
496
8128
33550336
8589869056
137438691328
2305843008139952128
2658455991569831744654692615953842176
191561942608236107294793378084303638130997321548169216

methods[0]

bigint(n, base=10)

Create a new bigint from n and a base. n can be a string, integer, or another bigint.

If you pass in a string you can set the base that string is encoded in.

.toString(base=10)

Print out the bigint instance in the requested base as a string.

bigint.fromBuffer(buf, opts)

Create a new bigint from a Buffer.

The default options are: { order : 'forward', // low-to-high indexed word ordering endian : 'big', size : 1, // number of bytes in each word }

Note that endian doesn't matter when size = 1.

methods[1]

For all of the instance methods below you can write either

bigint.method(x, y, z)

or if x is a bigint instance``

x.method(y, z)

.destroy()

Destroy a bigint. This module was previously using node-ffi and the GC hooks haven't been hacked in yet. You only need to call this if you're creating bigints in a loop. In the future this function will do nothing.

.toNumber()

Turn a bigint into a Number. If the bigint is too big you'll lose precision or you'll get ±Infinity.

.toBuffer(opts)

Return a new Buffer with the data from the bigint.

The default options are: { order : 'forward', // low-to-high indexed word ordering endian : 'big', size : 1, // number of bytes in each word }

Note that endian doesn't matter when size = 1.

.add(n)

Return a new bigint containing the instance value plus n.

.sub(n)

Return a new bigint containing the instance value minus n.

.mul(n)

Return a new bigint containing the instance value multiplied by n.

.div(n)

Return a new bigint containing the instance value integrally divided by n.

.abs()

Return a new bigint with the absolute value of the instance.

.neg()

Return a new bigint with the negative of the instance value.

.cmp(n)

Compare the instance value to n. Return a positive integer if > n, a negative integer if < n, and 0 if == n.

.gt(n)

Return a boolean: whether the instance value is greater than n (> n).

.ge(n)

Return a boolean: whether the instance value is greater than or equal to n (>= n).

.eq(n)

Return a boolean: whether the instance value is equal to n (== n).

.lt(n)

Return a boolean: whether the instance value is less than n (< n).

.le(n)

Return a boolean: whether the instance value is less than or equal to n (<= n).

.and(n)

Return a new bigint with the instance value bitwise AND (&)-ed with n.

.or(n)

Return a new bigint with the instance value bitwise inclusive-OR (|)-ed with n.

.xor(n)

Return a new bigint with the instance value bitwise exclusive-OR (^)-ed with n.

.pow(n)

Return a new bigint with the instance value raised to the nth power.

.powm(n, m)

Return a new bigint with the instance value raised to the nth power modulo m.

.invertm(m)

Compute the multiplicative inverse modulo m.

.rand()

.rand(upperBound)

If upperBound is supplied, return a random bigint between the instance value and upperBound - 1, inclusive.

Otherwise, return a random bigint between 0 and the instance value - 1, inclusive.

.probPrime()

Return whether the bigint is:

• certainly prime (true)
• probably prime ('maybe')
• certainly composite (false)

using mpz_probab_prime.

.nextPrime()

Return the next prime greater than this using mpz_nextprime.

.sqrt()

Return a new bigint that is the square root. This truncates.

.root(n)

Return a new bigint that is the nth root. This truncates.

install

You'll need the libgmp source to compile this package. Under Debian-based systems,

sudo aptitude install libgmp3-dev

On a Mac with Homebrew,

brew install gmp

And then install with npm:

npm install bigint