   ///
   ///     var numbers = [2.5, 21.25, 3.0, .nan, -9.5]
   ///     numbers.sort { !$1.isTotallyOrdered(belowOrEqualTo: $0) }
-  ///     // numbers == [-9.5, 2.5, 3.0, 21.25, NaN]
+  ///     print(numbers)
+  ///     // Prints "[-9.5, 2.5, 3.0, 21.25, nan]"
   ///
   /// The `isTotallyOrdered(belowOrEqualTo:)` method implements the total order
   /// relation as defined by the [IEEE 754 specification][spec].

/// Next, the observations in Celsius are converted to Fahrenheit:
///
///     let tempsFahrenheit = tempsCelsius.map { $0 * 1.8 + 32 }
///     // tempsFahrenheit == [70.7, 66.65, 80.6, nan, 82.85, nan, 73.4]
///
/// The NaN values in the `tempsCelsius` array are propagated through the
/// conversion and remain NaN in `tempsFahrenheit`.

///
///     let temperatureData = ["21.5", "19.25", "27", "no data", "28.25", "no data", "23"]
///     let tempsCelsius = temperatureData.map { Double($0) ?? .nan }
///     print(tempsCelsius)
///     // Prints "[21.5, 19.25, 27, .nan, 28.25, .nan, 23.0]"
///
///
/// Note that some elements in the `temperatureData ` array are not valid
/// numbers. When these invalid strings are parsed by the `Double` failable
