In functional list manipulation, what do we call "inserting something between each item"?

Occasionally I find I need to process a list by inserting a new item after each item, except the last one. Similar to how you might put a comma between each item of a list of strings. I got fed up of coding the special case for the last (or first) item every time, so I captured the pattern in a Linq-style extension: ``` public static IEnumerable<T> Separate<T>(this IEnumerable<T> source, Func<T> separator) { bool first = true; foreach (T item in source) { if (first) first = false; else yield return separator(); yield return item; } } ``` For example, this allows me to easily programatically fill a flow document with hyperlinks, but with a line-break between each one: ``` para.Inlines.AddRange(_recentFiles.Select(f => f.ToHyperlink()) .Separate(() => new LineBreak())); ``` Assuming this doesn't already exist in System.Linq.Enumerable (which is what I typically discover immediately after writing something like this), the question is, what is this `Separate` operation on lists usually called in other functional frameworks or languages?