Swift-BigInt 是 Swift 5 的轻量级易于使用的任意精度算术库。
它支持大多数常见数学运算符的整数（BInt）和分数（BDouble）。 还实现了优化的数学函数，例如阶乘或gcd，并可通过 BIntMath 访问。
计算 斐波那契数列（Fibonacci sequence），不受长整型位数限制。
从 https://codeload.github.com/mkrd/Swift-BigInt/zip/refs/heads/master
下载 Swift-BigInt-master.zip 解压后请看 Swift-BigInt-master/docs/index.html
cd D:\Swift\test
mkdir fibonacci
cd fibonacci
swift package init --type executable
Creating executable package: fibonacci
Creating Package.swift
Creating .gitignore
Creating Sources/
Creating Sources\main.swift
---
编写 Sources\main.swift 如下
// The Swift Programming Language
// file:///D:/Swift/test/Swift-BigInt-master/docs/index.html
import Foundation
import BigNumbervar i:Int = 0
if CommandLine.arguments.count > 1 {let str = CommandLine.arguments[1]let number = NumberFormatter().number(from: str)i = number!.intValue
} else {print(" usage: fibonacci.exe n ")exit(0)
}
// 计算 斐波那契数列（Fibonacci sequence）
func fib(n: Int) -> BInt {if n <= 0 { return 0 } var x: BInt = 0, y: BInt = 1for _ in 1..<n {(x, y) = (y, y + x)}return y
}
// 调用示例
print("fib(\(i))=", fib(n:i))
编写 fibonacci\Package.swift 如下
// swift-tools-version: 5.10
// The swift-tools-version declares the minimum version of Swift required to build this package.import PackageDescriptionlet package = Package(name: "fibonacci",//products: [ ],dependencies: [.package(url: "https://github.com/mkrd/Swift-BigInt.git", branch: "master")],targets: [// Targets are the basic building blocks of a package, defining a module or a test suite.// Targets can depend on other targets in this package and products from dependencies..executableTarget(name: "fibonacci",dependencies: [ ],plugins: [.plugin(name: "BigNumber", package: "Swift-BigInt"),]),]
)
cd fibonacci
编译当前包及其依赖项：
swift build
D:\Swift\test\fibonacci>swift build
Building for debugging...
[13/13] Linking D:\Swift\test\fibonacci\.build\x86_64-unknown-windows-msvc\debug\fibonacci.exe
Build complete! (28.21s)
warning: unable to create symbolic link at D:\Swift\test\fibonacci\.build\debug: cd D:\Swift\test\fibonacci\.build\x86_64-unknown-windows-msvc\debug\
运行 fibonacci.exe 200
fib(200)= 280571172992510140037611932413038677189525
运行 fibonacci.exe 1000
fib(1000)= ......
用 python 校验，以上结果正确：
python fibonacci.py 200
fib1(200)= 280571172992510140037611932413038677189525
这是本人练习笔记，仅供同学参考。
参阅：全面掌握 Swift 包依赖管理工具 —— 命令行、Manifest API、Xcode、二进制包、集合、插件
