Add fuzzy numbers and modularize

Package.swift

@@ -3,12 +3,30 @@
 
 import PackageDescription
 
+enum SubmoduleName: String {
+    case fuzzyKit = "FuzzyKit"
+    case fuzzySets = "FuzzySets"
+    case fuzzyNumbers = "FuzzyNumbers"
+    
+    var name: String { rawValue }
+    var target: String { rawValue }
+    var testTarget: String { rawValue + "Tests" }
+}
+
 let package = Package(
     name: "FuzzyKit",
     products: [
         .library(
-            name: "FuzzyKit",
-            targets: ["FuzzyKit"]
+            name: SubmoduleName.fuzzyKit.name,
+            targets: [SubmoduleName.fuzzyKit.target]
+        ),
+        .library(
+            name: SubmoduleName.fuzzySets.name,
+            targets: [SubmoduleName.fuzzySets.target]
+        ),
+        .library(
+            name: SubmoduleName.fuzzyNumbers.name,
+            targets: [SubmoduleName.fuzzyNumbers.target]
         ),
     ],
     dependencies: [
@@ -16,14 +34,35 @@ let package = Package(
     ],
     targets: [
         .target(
-            name: "FuzzyKit",
+            name: SubmoduleName.fuzzyKit.target,
+            dependencies: [
+                .target(name: SubmoduleName.fuzzySets.target),
+                .target(name: SubmoduleName.fuzzyNumbers.target),
+            ]
+        ),
+        .target(
+            name: SubmoduleName.fuzzySets.target,
             dependencies: [
                 .product(name: "RealModule", package: "swift-numerics"),
             ]
         ),
         .testTarget(
-            name: "FuzzyKitTests",
-            dependencies: ["FuzzyKit"]
+            name: SubmoduleName.fuzzySets.testTarget,
+            dependencies: [
+                .target(name: SubmoduleName.fuzzySets.target)
+            ]
+        ),
+        .target(
+            name: SubmoduleName.fuzzyNumbers.target,
+            dependencies: [
+                .target(name: SubmoduleName.fuzzySets.target),
+            ]
+        ),
+        .testTarget(
+            name: SubmoduleName.fuzzyNumbers.testTarget,
+            dependencies: [
+                .target(name: SubmoduleName.fuzzyNumbers.target),
+            ]
         ),
     ]
 )

Sources/FuzzyKit/FuzzyKit.swift

@@ -0,0 +1,4 @@
+// A module that re-exports the complete FuzzyKit public API.
+
+@_exported import FuzzySets
+@_exported import FuzzyNumbers

Sources/FuzzyNumbers/FuzzyNumber.swift

@@ -0,0 +1,18 @@
+import FuzzySets
+
+public protocol FuzzyNumber {
+    
+    typealias Universe = Double
+    
+    func eraseToAnyFuzzySet() -> AnyFuzzySet<Universe>
+    
+    static func + (lhs: Self, rhs: Self) -> Self
+    
+    static func - (lhs: Self, rhs: Self) -> Self
+    
+    prefix static func - (x: Self) -> Self
+    
+//    func approximatelyMultiplied(by other: Self) -> Self
+//    
+//    func approximatelyDivided(by other: Self) -> Self
+}

Sources/FuzzyNumbers/Implementations/TriangularFuzzyNumber.swift

@@ -0,0 +1,65 @@
+import FuzzySets
+
+public struct TriangularFuzzyNumber: FuzzyNumber {
+    
+    public typealias Universe = Double
+    
+    public let minimum: Universe
+    public let peak: Universe
+    public let maximum: Universe
+    
+    internal let function: MembershipFunction<Universe>
+    
+    public init(minimum: Universe, peak: Universe, maximum: Universe) {
+        self.minimum = minimum
+        self.peak = peak
+        self.maximum = maximum
+        self.function = .triangular(minimum: minimum, peak: peak, maximum: maximum)
+    }
+    
+    public init(peak: Universe, leftInterval: Universe, rightInterval: Universe) {
+        self.minimum = peak - leftInterval
+        self.peak = peak
+        self.maximum = peak + rightInterval
+        self.function = .triangular(minimum: minimum, peak: peak, maximum: maximum)
+    }
+    
+    public func eraseToAnyFuzzySet() -> AnyFuzzySet<Universe> {
+        .init(membershipFunction: function)
+    }
+    
+    public static func + (lhs: TriangularFuzzyNumber, rhs: TriangularFuzzyNumber) -> TriangularFuzzyNumber {
+        .init(
+            minimum: lhs.minimum + rhs.minimum,
+            peak: lhs.peak + rhs.peak,
+            maximum: lhs.maximum + rhs.maximum
+        )
+    }
+    
+    public static func - (lhs: TriangularFuzzyNumber, rhs: TriangularFuzzyNumber) -> TriangularFuzzyNumber {
+        .init(
+            minimum: lhs.minimum - rhs.maximum,
+            peak: lhs.peak - rhs.peak,
+            maximum: lhs.maximum - rhs.minimum
+        )
+    }
+    
+    prefix public static func - (x: TriangularFuzzyNumber) -> TriangularFuzzyNumber {
+        .init(minimum: -x.maximum, peak: -x.peak, maximum: -x.minimum)
+    }
+    
+//
+//    public func approximatelyMultiplied(by other: TriangularFuzzyNumber) -> TriangularFuzzyNumber {
+//        // TODO
+//    }
+//
+//    public func approximatelyDivided(by other: TriangularFuzzyNumber) -> TriangularFuzzyNumber {
+//        // TODO
+//    }
+}
+
+extension TriangularFuzzyNumber: Equatable {
+    public static func == (lhs: TriangularFuzzyNumber, rhs: TriangularFuzzyNumber) -> Bool {
+        lhs.minimum == rhs.minimum && lhs.peak == rhs.peak && lhs.maximum == rhs.maximum
+    }
+}

Tests/FuzzyNumbersTests/TriangularFuzzyNumberTests.swift

@@ -0,0 +1,14 @@
+import XCTest
+import FuzzyNumbers
+
+final class TriangularFuzzyNumberTests: XCTestCase {
+    func test_addition() {
+        let a = TriangularFuzzyNumber(minimum: -3, peak: 2, maximum: 4)
+        let b = TriangularFuzzyNumber(minimum: -1, peak: 0, maximum: 6)
+        let expect = TriangularFuzzyNumber(minimum: -4, peak: 2, maximum: 10)
+        
+        let result = a + b
+        
+        XCTAssertEqual(result, expect)
+    }
+}

Tests/FuzzySetsTests/AnyFuzzySetTests.swift

@@ -1,5 +1,5 @@
 import XCTest
-import FuzzyKit
+import FuzzySets
 
 final class AnyFuzzySetTests: XCTestCase {
     func test_initFromDiscreteMutableFuzzySet() {

Tests/FuzzySetsTests/DiscreteMutableFuzzySetTests.swift

@@ -1,5 +1,5 @@
 import XCTest
-import FuzzyKit
+import FuzzySets
 
 final class DiscreteMutableFuzzySetTests: XCTestCase {
     func test_defaultInit_allGradesAreZero() throws {

Tests/FuzzySetsTests/FunctionsTests/MembershipFunctionTests.swift

@@ -1,5 +1,5 @@
 import XCTest
-import FuzzyKit
+import FuzzySets
 
 final class MembershipFunctionTests: XCTestCase {
     func test_isCallable() throws {

Tests/FuzzySetsTests/Helpers/Helpers.swift

@@ -1,5 +1,5 @@
 import XCTest
-import FuzzyKit
+import FuzzySets
 
 func XCTAssertApproximatelyEqual(_ v1: Double, _ v2: Double, tolerance: Double = 0.0001) {
     let diff = v1 - v2

Tests/FuzzySetsTests/IterableFuzzySetTests.swift

@@ -1,5 +1,5 @@
 import XCTest
-import FuzzyKit
+import FuzzySets
 
 class IterableFuzzySetTests: XCTestCase {
     private var near4Support4: [IterableFuzzySet<Int, StrideThrough<Int>>.Element] = [