Distinction between iterator and enumerator

Question

An interview question for a .NET 3.5 job is \"What is the difference between an iterator and an enumerator\"?

This is a core distinction to make, what with LINQ, etc

Answer 1

What C# calls an iterator is more commonly (outside of the C# world) called a generator or generator function (e.g. in Python). A generator function is a specialized case of coroutine. A C# iterator (generator) is a special form of an enumerator (a data type implementing the IEnumerable interface).

I dislike this usage of the term iterator for a C# generator because it is just as much an enumerator as it is an iterator. Too late for Microsoft to change its mind though.

For contrast consider that in C++ an iterator is a value which is used primarily to access sequential elements in a collection. It can be advanced, derferenced to retrieve a value, and tested to see whether the end of the collection has been reached.

Answer 2

Enumeration deals with objects while iteration deals with values only. Enumeration is used when we use vector hashtable etc while iteration are used in while loop for loop etc. I've never use the yield keyword so I couldn't tell you.

Answer 3

Iteration deals with arrays and strings while iteration deals with objects

In JavaScript you can iterate an array or a string with :

• forEach Loop
• for loop
• for of Loop
• do while Loop
• while Loop

And you can enumerate an object with :

• for in Loop
• Object.keys() Method
• Object.values() Method
• Object.entries() Method