Every Day – The Daily WTF

There are real advantages to taking a functional programming approach to expressing problems. Well, some problems, anyway.

Kevin sends us this example of elegant, beautiful functional code in C#:

List dates = Enumerable.Range
  (0, 1 + settings.EndDate.Subtract   
  (settings.BeginDate).Days).Select
  (offset => settings.BeginDate.AddDays(offset)).ToList();
foreach (DateTime procDate in dates)
{

}

If you’re not sure what this code does, it’s okay- Kevin rewrote it and “ruined” it:

DateTime procDate = settings.BeginDate;
while(procDate <= settings.EndDate)
{

procDate= procDate.AddDays(1);
}

The goal of this code is simply to do something for every day within a range of dates. These two approaches vary a bit in terms of readability though.

I guess the loop in the functional version isn’t mutating anything, I suppose. But honestly, I’m surprised that this didn’t take the extra step of using the .ForEach function (which takes a lambda and applies it to each parameter). Heck, with that approach, they could have done this whole thing in a single statement.