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Pure Math in Pure Swift.
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Tests RationalNumber etc made ExpByInt. Nov 5, 2019
doc update README. Apr 5, 2018
.gitignore delete xcodeprojs. Apr 4, 2018
LICENSE change license to MIT. Nov 5, 2019
Package.swift Sample -> SwiftyMathSample. Oct 9, 2019
README.md

README.md

SwiftyMath

ss1

The aim of this project is to understand Mathematics by realizing abstract concepts as codes. Mathematical axioms correspond to protocols, and objects satisfying some axioms correspond to structs.

Submodules

Getting Started

Using SwiftyMathREPL

ss2

Creating Your Own Project

1. Initialize a Package

$ mkdir YourProject
$ cd YourProject
$ swift package init --type executable

2. Edit Package.swift

 // swift-tools-version:5.1
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
 
 let package = Package(
     name: "YourProject",
     dependencies: [
         // Dependencies declare other packages that this package depends on.
-        // .package(url: /* package url */, from: "1.0.0"),
+        .package(url: "https://github.com/taketo1024/SwiftyMath.git", from: "1.0.0"),
     ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages which this package depends on.
         .target(
             name: "YourProject",
-            dependencies: []),
+            dependencies: ["SwiftyMath"]),
     ]
 )

3. Edit Sources/YourProject/main.swift

import SwiftyMath

let a = RationalNumber(4, 5)  // 4/5
let b = RationalNumber(3, 2)  // 3/2

print(a + b)     // 23/10

4. Run

$ swift run
 23/10

Using Mathematical Symbols

We make use of mathematical symbols such as sets 𝐙, 𝐐, 𝐑, 𝐂 and operators ⊕, ⊗ etc. Copy the folder CodeSnippets to ~/Library/Developer/Xcode/UserData/ then you can quickly input these symbols by the completion of Xcode.

ss3.png

Examples

Rational Numbers

let a = 𝐐(4, 5)  // 4/5
let b = 𝐐(3, 2)  // 3/2

a + b  // 23/10
a * b  // 6/5
b / a  // 15/8

Matrices

typealias M = SquareMatrix<_2, 𝐙> // Matrix of integers with fixed size 2×2.

let a = M(1, 2, 3, 4)  // [1, 2; 3, 4]
let b = M(2, 1, 1, 2)  // [2, 1; 1, 2]

a + b  // [3, 3; 4, 6]
a * b  // [4, 5; 10, 11]

a + b == b + a  // true: addition is commutative
a * b == b * a  // false: multiplication is noncommutative

Permutation (Symmetric Group)

typealias S_5 = Permutation<_5>

let s = S_5(cyclic: 0, 1, 2) // cyclic notation
let t = S_5([0: 2, 1: 3, 2: 4, 3: 0, 4: 1]) // two-line notation

s[1]  // 2
t[2]  // 4

(s * t)[3]  // 3 -> 0 -> 1
(t * s)[3]  // 3 -> 3 -> 0

Polynomials

typealias P = Polynomial<𝐐>

let f = P(0, 2, -3, 1) // x^3 − 3x^2 + 2x
let g = P(6, -5, 1)    // x^2 − 5x + 6
    
f + g  // x^3 - 2x^2 - 3x + 6
f * g  // x^5 - 8x^4 + 23x^3 - 28x^2 + 12x
f % g  // 6x - 12
    
gcd(f, g) // 6x - 12

Integer Quotients, Finite Fields

typealias Z_4 = IntegerQuotientRing<_4>
Z_4.printAddTable()
+   |   0   1   2   3
----------------------
0   |   0   1   2   3
1   |   1   2   3   0
2   |   2   3   0   1
3   |   3   0   1   2
typealias F_5 = IntegerQuotientField<_5>
F_5.printMulTable()
*   |   0   1   2   3   4
--------------------------
0   |   0   0   0   0   0
1   |   0   1   2   3   4
2   |   0   2   4   1   3
3   |   0   3   1   4   2
4   |   0   4   3   2   1

Algebraic Extension

// Construct an algebraic extension over 𝐐:
// K = 𝐐(√2) = 𝐐[x]/(x^2 - 2).

struct p: _Polynomial {                            // p = x^2 - 2, as a struct
    typealias K = 𝐐
    static let value = Polynomial<𝐐>(-2, 0, 1)
}

typealias I = PolynomialIdeal<p>                   // I = (x^2 - 2)
typealias K = QuotientField<Polynomial<𝐐>, I>      // K = 𝐐[x]/I

let a = Polynomial<𝐐>(0, 1).asQuotient(in: K.self) // a = x mod I
a * a == 2                                         // true!

License

Swifty Math is released under MIT license.

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