c#-lazy-sequences.cs

using System.Linq;

class Foo {
	static void Main(string[] _) {

		var xs = new[] {"apple", "passionfruit", "banana", "mango", "pear",};

		/* https://msdn.microsoft.com/en-us/library/9eekhta0 */

		var ys = xs
			.Take(4)
			.Select(x => x.ToUpper()) /* map */
			.Where(x => x.Length < 6) /* filter */
			.SelectMany(x => x) /* joiner */
			.Take(9);

		System.Diagnostics.Trace.Assert(
			ys.SequenceEqual("APPLEMANG"));

		System.Console.WriteLine(ys.ToArray());

	}
}