dankogai/swift-bigint-javascriptcore

Synopsis

import JSCBigInt

// Integer literals of any size, thanks to StaticBigInt
let n: JSBigInt = 123456789012345678901234567890123456789012345678901234567890

// A full SignedInteger: use it like any Swift integer
let fact100 = (1...100).map { JSBigInt($0) }.reduce(1, *)
JSBigInt(2).power(128)              // 340282366920938463463374607431768211456
(JSBigInt(1) << 100) >> 100         // 1
JSBigInt("deadbeef", radix: 16)!    // 3735928559
fact100.toString(radix: 36)         // "1cnfrwcnvxbzzicfd6…"
Int(JSBigInt(42))                   // 42 — stdlib conversions just work
Double(JSBigInt(1) << 100)          // 1.2676506002282294e+30

Usage

Add to your Package.swift:

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

and import JSCBigInt.

Features

• JSBigInt conforms to SignedInteger (hence BinaryInteger, Numeric,

Comparable, Hashable, Strideable…), so it works with generic integer algorithms out of the box.

• Integer literals use StaticBigInt — no precision loss, no strings needed.
• Swift semantics throughout: / truncates toward zero, % takes the

dividend's sign, >> is an arithmetic (smart) shift, division by zero traps.

• String conversion to and from any radix in 2...36.
• Exact conversions to and from BinaryInteger and BinaryFloatingPoint

types, including two's-complement words for stdlib interop.

• power(_:) via the JS ** operator, and modular exponentiation

power(_:mod:) with swift-bignum-compatible semantics (least non-negative residue; a negative exponent takes the modular inverse).

• greatestCommonDivisor(with:) and squareRoot() (integer square

root, floor), named and behaving like their swift-bignum and attaswift/BigInt counterparts.

• The whole primality kit, ported from swift-bignum with identical

verdicts: isPrime is tri-state — false and true are proofs (below 2⁶⁴ via exhaustively-verified [Baillie-PSW], below [A014233]'s last entry ≈3.3 × 10²⁴ via thirteen Miller-Rabin bases, or for any Mersenne number via Lucas-Lehmer), nil means "probably prime, unproven" with isProbablePrime (BPSW) holding that opinion and isSurelyPrime giving both halves at once. The building blocks are public too: millerRabinTest(base:), isLucasProbablePrime, isMersennePrime, and jacobiSymbol(_:). nextPrime/prevPrime walk to the neighboring primes (on the probable test, so they terminate at any size), each walk in a single bridge crossing, and JSBigInt.primes is the endless lazy sequence of them: Array(JSBigInt.primes.prefix(5)) is [2, 3, 5, 7, 11].

[Baillie-PSW]: https://en.wikipedia.org/wiki/Baillie%E2%80%93PSW_primality_test

[A014233]: https://oeis.org/A014233

• Codable (encoded as a decimal string).
• Thread-safe: values are immutable and JavaScriptCore serializes access

through the JSVirtualMachine lock.

Caveats

• Apple platforms only (macOS, iOS, tvOS, visionOS). No Linux, no watchOS —

they lack JavaScriptCore.

• Every operation crosses the Swift ⇄ JavaScriptCore bridge, so it is not a

speed demon for many small operations. Large-number performance is excellent, though — for 10k-digit multiplication it beats the pure-Swift bignum libraries (attaswift/BigInt, dankogai/swift-bignum) severalfold, since the heavy lifting happens inside JSC's optimized BigInt. See Benchmark.md for numbers.

• For serious work, consider [attaswift/BigInt] or [dankogai/swift-bignum] —

or [dankogai/swift-bigint-gmp], the identical API on GNU MP, which beats all three (this one included) at nearly every size; its Benchmark.md races the four together. This package is a proof of concept that happens to be practical.

[attaswift/BigInt]: https://github.com/attaswift/BigInt [dankogai/swift-bignum]: https://github.com/dankogai/swift-bignum [dankogai/swift-bigint-gmp]: https://github.com/dankogai/swift-bigint-gmp

Prerequisite

Swift 5.9 or better, macOS 14 / iOS 17 or later.

License

MIT. See LICENSE.

Package Metadata

Repository: dankogai/swift-bigint-javascriptcore

Default branch: main

README: README.md