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+:toc: left
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+= Int.01 -- Digits Sequence
+
+A simple, first assignment for implementing interfaces.
+We did something very similar together in the workshop, so this exercise should be easy to solve for you.
+
+Your task is to implement a class which takes a number and:
+
+. Allows iteration over its digits => `IEnumerable`
+. Can compare two digits => `IComparable`
+
+[plantuml]
+----
+@startuml
+hide empty fields
+hide empty methods
+
+class Digits <<sealed>> {
+    -int _number [readonly]
+
+    +Digits(int)
+    +int CompareTo(Digits?)
+    +IEnumerator<int> GetEnumerator()
+    +IEnumerator IEnumerable.GetEnumerator()
+    +string ToString() [override]
+}
+
+class DigitEnumerator <<sealed>> {
+    -int _number [readonly]
+    +int Current [readonly]
+    +object IEnumerator.Current [readonly]
+
+    +DigitEnumerator(int)
+    +bool MoveNext()
+    +void Reset()
+    +Dispose()
+}
+
+interface IEnumerable<int> {
+    {abstract} +IEnumerator<int> GetEnumerator()
+    {abstract} +IEnumerator IEnumerable.GetEnumerator()
+}
+interface IComparable<Digits> {
+    {abstract} +int CompareTo(Digits?)
+}
+interface IEnumeratorNG {
+    {abstract} +object Current [readonly]
+
+    {abstract} +bool MoveNext()
+    {abstract} +void Reset()
+}
+note bottom: Actual name is just 'IEnumerator'\n using NG postfix due to PlantUML issue
+interface IEnumerator<int> {
+    {abstract} +int Current [readonly]
+}
+interface IDisposable {
+    {abstract} +Dispose()
+}
+
+IEnumerable <|-- Digits
+IComparable <|-- Digits
+IEnumerator <|-- DigitEnumerator
+IEnumeratorNG <|-- IEnumerator
+IDisposable <|-- IEnumerator
+
+@enduml
+----
+
+== Implementation Requirements
+=== `DigitEnumerator`
+
+* Implements `IEnumerator<int>`
+* Negative numbers are simply converted to positive ones
+** e.g. -899 => 899
+* _Can_ be reset
+* `IEnumerator.Current` should be trivial
+* `Dispose`
+** Part of the `IDisposable` interface we received transitively
+** Used to release resources -- will become very important in the future!
+** https://learn.microsoft.com/en-us/dotnet/api/system.idisposable?view=net-9.0[Read through the documentation]
+** You should now have realized what you have to implement here in this case 😉
+* *Important:*
+** Relying on the compiler to generate a state machine will not always be possible (in complex scenarios)
+** Also, you have to proof that you can do it yourself
+** => Implement the enumerator _without_ using `yield`!
+* Implement it _without_ using a string!
+* Example: Number 91302 => 9, 1, 3, 0, 2
+
+TIP: Some additional, private fields, properties or maybe even methods might be useful
+
+=== `Digits`
+
+* Implements `IEnumerable<int>` & `IComparable<Digits>`
+* Negative numbers are simply converted to positive ones
+** Same as for the enumerator
+* `CompareTo`
+** Create a _clean_ implementation which checks for same and null references _before_ doing the actual comparison
+* `GetEnumerator` has to make use of `DigitEnumerator`
+* `IEnumerable.GetEnumerator` should be trivial
+* `ToString`
+** Just for good practice make sure the string output if formatted for the _invariant_ culture
+
+== Tasks
+
+. Complete the implementation according to the specified requirements
+. Create the XMLDoc for the application -- _think_ which comments are required and which might already be present
+
+NOTE: Unit tests have been provided with the starter code