Question

I learned the intersperse function from Haskell, and have been looking for an implementation in c#.

Intersperse takes 2 arguments, an IEnumerable<T> source and a T element. It returns an IEnumerable with element inserted between every element of source.

One possible use-case is to put an arbitrary integer in between a list of integers, for example:

// returns: {1, 0, 2, 0, 3} (List<int>() {1, 2, 3}).Intersperse(0); 

This is a general case of string.Join(…).

Answer 1

Something the others have missed: if you only want it in between items, and not also in front or behind, you need to do an extra check:

public static IEnumerable<T> Intersperse<T>(this IEnumerable<T> source, T element) {     bool first = true;     foreach (T value in source)     {         if (!first) yield return element;         yield return value;         first = false;     } } 

or

public static IEnumerable<T> Intersperse<T>(this IEnumerable<T> source, T element) {     var e = source.GetEnumerator();      bool b = e.MoveNext();     if (b) yield return e.Current;      while (e.MoveNext())     {         yield return element;         yield return e.Current;     } }