feature: adds NadalaNumber model

Author: bjacobgordon

NumberSystems/Sources/NumberSystems/Positional/Models/NadalaNumber.swift

@@ -0,0 +1,30 @@
+public struct NadalaNumber: PositionalNumberSystemizable {
+    public enum Digit: Int {
+        case               tɑ
+        case  no , nɛ, nu, nɑ
+        case `do`, dɛ, du, dɑ
+        case  lo , lɛ, lu, lɑ
+    }
+}
+
+extension NadalaNumber.Digit: PositionalDigitSystemizable {
+    public static var placeholder: Self { .tɑ }
+    
+    public var predecessor: Self {
+        switch self {
+        case .lɑ: return .lu
+        case .lu: return .lɛ
+        case .lɛ: return .lo
+        case .lo: return .dɑ
+        case .dɑ: return .du
+        case .du: return .dɛ
+        case .dɛ: return .do
+        case .do: return .nɑ
+        case .nɑ: return .nu
+        case .nu: return .nɛ
+        case .nɛ: return .no
+        case .no: return .placeholder
+        default : Self.fatalPredecessionError()
+        }
+    }
+}

NumberSystems/Tests/NumberSystemsTests/NadalaNumberTests.swift

@@ -0,0 +1,8 @@
+import Testing
+@testable import NumberSystems
+
+@Test func quantitiesOfNadalaDigits() async throws {
+    NadalaNumber.Digit.allCases.forEach {
+        #expect($0.quantityMatchesCardinality)
+    }
+}