Allow Double to use equality minus epsilon comparison

Sources/Number/Double+NYPLAdditions.swift

@@ -0,0 +1,22 @@
+//
+//  Created by Ettore Pasquini on 11/29/24.
+//  Copyright © 2024 The New York Public Library. All Rights Reserved.
+//
+
+import Foundation
+
+infix operator =~= : ComparisonPrecedence
+
+public extension Double {
+
+  /// Performs equality check minus an epsilon
+  /// - Returns: `true` if the numbers differ by less than the epsilon,
+  /// `false` otherwise.
+  static func =~= (a: Double, b: Double?) -> Bool {
+    guard let b = b else {
+      return false
+    }
+
+    return abs(a - b) < Double.ulpOfOne
+  }
+}