bignum-lua

Large number library that trades precision for simplicity. Number range is ±10^(2^53).

Features

• Arithmetic operations: addition, subtraction, multiplication, division, exponentiation
• Additional operations: to-string, cloning, comparison, negation, inversion, absolute value
• Small (< 200 sloc)
• Portable (works in Lua 5.1+)

How to use

First, require the library to load it, preferably into a local variable named bignum.

local bignum = require "bignum"

To create a bignum, supply zero, one, or two numbers to bignum.new. The first number represents the significand, while the second represents the power of 10. Both default to 0 if absent.

local x = bignum.new()     --> 0
local y = bignum.new(123)  --> 123
local z = bignum.new(4, 5) --> 400000

It is also possible to call bignum directly:

local x = bignum()     --> 0
local y = bignum(123)  --> 123
local z = bignum(4, 5) --> 400000

For operations on bignums, there are a few choices of syntax:

local w = bignum.add(y, z)
local w = y:add(z)
local w = y + z

All of these will result in variable w having the value 400123.

Please see the source code for other method names.

Warnings

The following will result in the library having undefined behavior:

• Supplying invalid arguments to bignum.new
• Manually changing the value of items within a bignum
• Exceeding the number range

It is up to you to make sure that your code avoids these things.