A Useful Linq Extension Method: Intersperse
Have you ever had a case where you want to insert a constant item in-between each element of a list of items? For example, if I’ve got a list of numbers:
1,2,3,4,5
And I want to insert 0 between each one to get:
1,0,2,0,3,0,4,0,5
Meet my friend Intersperse (stolen from Haskell, if you hadn’t guessed):
var items = new[] {1, 2, 3, 4, 5}.Intersperse(0).ToArray();
foreach (var item in items)
{
Console.Write(item);
}This code outputs:
102030405
And here is the Intersperse extension method:
public static IEnumerable<T> Intersperse<T>(this IEnumerable<T> items, T separator)
{
var first = true;
foreach (var item in items)
{
if (first) first = false;
else
{
yield return separator;
}
yield return item;
}
}
Some interesting uses. System.String is, of course, an array of char, so you can do this:
var doubleSpaced = new string("hello world".Intersperse(' ').ToArray());
Console.WriteLine(doubleSpaced);
// outputs 'h e l l o w o r l d'Or how about this perennial problem, creating a comma separated list:
var strings = new[] {"one", "two", "three"};
var commaSeprated = new string(strings.Intersperse(",").Concat().ToArray());
Console.WriteLine(commaSeprated);
// outputs one,two,three
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