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Arbitrary-precision arithmetic for Swift, in Swift
.package(url: "https://github.com/dankogai/swift-bignum.git", from: "5.2.3")

Swift 5 MIT LiCENSE build status


Arbitrary-precision arithmetic for Swift, in Swift


import BigNum
BigRat.sqrt(2, precision:128)  // 240615969168004511545033772477625056927/170141183460469231731687303715884105728
BigFloat.exp(1, precision:128) // 2.718281828459045235360287471352662497759


This module offers two flavors of Arbitrary-precision types that conforms to FloatingPoint.

  • BigRat - Arbitrary-precision rational number.
  • BigFloat - Arbitrary-precision floating point.

In addition to all arithmetic operations that FloatingPoint supports. Most of the functions in <math.h> are offered as static functions. As you see in the synopsis above, all arithmetic functions and operators that are lossy can take precision:Int as an optional argument. When omitted the value of BigRat.precision or BigFloat.precision is used (default:64)

BigInt, an arbitrary-precision interger type is internally used and re-exported so you don't have to import BigInt just for that. BigInt is also extended with .over() method so instead of constructing BigRat directly, you can:

BigInt(3260954456333195553).over(BigInt(2305843009213693952)) // == BigRat.sqrt(2)



$ git clone https://github.com/dankogai/swift-bignum.git
$ cd swift-complex # the following assumes your $PWD is here
$ swift build



$ scripts/run-repl.sh


$ swift run --repl

and in your repl,

Welcome to Apple Swift version 4.2 (swiftlang-1000.11.37.1 clang-1000.11.45.1). Type :help for assistance.
  1> import BigNum 
  2> BigRat.sqrt(2, precision:128)
$R0: BigNum.BigRat = {
  num = {
    magnitude = {
      kind = array
      storage = 2 values {
        [0] = 6448461645324402335
        [1] = 13043817825332782212
    sign = plus
  den = {
    magnitude = {
      kind = array
      storage = 2 values {
        [0] = 0
        [1] = 9223372036854775808
    sign = plus


Xcode project is deliberately excluded from the repository because it should be generated via swift package generate-xcodeproj . For convenience, you can

$ scripts/xcode-prep

And the Workspace opens up for you with Playground on top. The playground is written as a manual.

From Your SwiftPM-Managed Projects

Add the following to the dependencies section:

  url: "https://github.com/dankogai/swift-bignum.git", .branch("main")

and the following to the .target argument:

  name: "YourSwiftyPackage",
  dependencies: ["BigNum"])

Now all you have to do is:

import BigNum

in your code. Enjoy!


Swift 5 or better, OS X or Linux to build.

Depends on attaswift/BigInt for internal representation of BigFloat and BigRat.

Depends on apple/swift-numerics since version 5.1 for the ElementaryFunctions protocol. Prior versions depended on dankogai/swift-floatingpoint for the FloatingPointMath protocols but it is replaced by the ElementaryFunctions.


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