Is yield useful outside of LINQ?

Question

When ever I think I can use the yield keyword, I take a step back and look at how it will impact my project. I always end up returning a collection instead of yeilding becau

Answer 1

Yield is very useful in general. It's in ruby among other languages that support functional style programming, so its like it's tied to linq. It's more the other way around, that linq is functional in style, so it uses yield.

I had a problem where my program was using a lot of cpu in some background tasks. What I really wanted was to still be able to write functions like normal, so that I could easily read them (i.e. the whole threading vs. event based argument). And still be able to break the functions up if they took too much cpu. Yield is perfect for this. I wrote a blog post about this and the source is available for all to grok :)

Answer 2

I do understand its usefulness in linq, but I feel that only the linq team is writing such complex queriable objects that yield is useful.

Yield was useful as soon as it got implemented in .NET 2.0, which was long before anyone ever thought of LINQ.

Why would I write this function:

IList<string> LoadStuff() {
  var ret = new List<string>();
  foreach(var x in SomeExternalResource)
    ret.Add(x);
  return ret;
}

When I can use yield, and save the effort and complexity of creating a temporary list for no good reason:

IEnumerable<string> LoadStuff() {
  foreach(var x in SomeExternalResource)
    yield return x;
}

It can also have huge performance advantages. If your code only happens to use the first 5 elements of the collection, then using yield will often avoid the effort of loading anything past that point. If you build a collection then return it, you waste a ton of time and space loading things you'll never need.

I could go on and on....