[masklinn]

> C# has them, and so does Scala.

With the slight difference that its generics are reified, so all `Function` generic arities have the same name (it's `Function<T>`, `Function<T1, T2>`, ...), although because there is no `void` or `Unit` type in C# it needs two base function types, to handle functions with a return value (`Function`) and functions with no return value (`Action`).

I believe the Kotlin project fixes this issue by having a first-class `Unit` type, so C#'s `Action` becomes `Func<Unit>` in Kotlin.

[StrawberryFrog]

C#'s type system is a bit messy over there. Besides Func<T> and Action<T>, there's also Predicate<T> , which works the same as Func<T, bool> except for being an entirely different type that's non-trivial to cast to Func<T, bool>. And the whole lot look a lot like delegates.

If they were all just Func<T> (or aliases for that, or wrappers over that when multicast is really needed), it would be a lot simpler.

[jawher]

Even Java has the Void type, meaning you can write:

    Function<Void>

It's a bit shady though as you still have to return a value from the body of the method, and that value has to be null.

[StrawberryFrog]

That sort of this is also easy to do in C# or any strongly typed language. Similar things in c# are the DBNull type which "Represents a nonexistent value" from a database (http://msdn.microsoft.com/en-us/library/system.dbnull.aspx ) and Type.Missing which "Represents a missing value in the Type information"

[masklinn]

> It's a bit shady though

'bit of an understatement there.