It’s the function composition operator. More info on Chris Smith’s blogpost. Introducing the Function Composition operator (>>): let inline (>>) f g x = g(f x) Which reads as: given two functions, f and g, and a value, x, compute the result of f of x and pass that result to g. The interesting thing … Read more
The usual idiom is to define the function to take one argument of type Unit (let functionName () = 42). It will then be called as functionName (). (The unit type has only one value, which is ().)
In order to switch ASP.NET Core 3.0 back to use JSON.NET, you will need to reference the Microsoft.AspNetCore.Mvc.NewtonsoftJson NuGet package. That will contain the AddNewtonsoftJson extension method. In C#, this would look like this: services.AddControllers() .AddNewtonsoftJson(); So assuming that I understand enough of F#, I would say that your call would be correct if you … Read more
As the compiler points out, there is no type that can be assigned to x so that the expression (x x) is well-typed (this isn’t strictly true; you can explicitly type x as obj->_ – see my last paragraph). You can work around this issue by declaring a recursive type so that a very similar … Read more
You call them as instance methods: let Count (text : string) = let words = text.Split [|’ ‘|] let nWords = words.Length (nWords) (Note you need to use [| |] because Split takes an array not a list; or, as per Joel Mueller’s comment, because Split takes a params array, you can just pass in … Read more
Yes, it’s called if .. then .. else In fact in F# everything is an expression, even an if .. then .. else block. In C# var x = true ? 0 : 1; In F# let x = if true then 0 else 1 So in your case: let y = Seq.groupBy (fun x … Read more
You want to prevent your wife from aging by making her age immutable? 🙂 For a tuple that contains only two members, you can fst and snd to extract the members of the pair. let wifeName = fst myWife; let wifeAge = snd myWife; For longer tuples, you’ll have to unpack the tuple into other … Read more
If you want to avoid using the full name, you can use open in F#: open System let s = String.Format(“Hello {0}”, “world”) This should work in both F# interactive (enter the open clause first) and in normal compiled applications. The key thing is that you must write String with upper-case S. This is because … Read more
As others said, there is no such operator, because it wouldn’t make much sense. I actually think that this is a good thing, because it makes it easier to realize that the operation will not be efficient. In practice, you shouldn’t need the operator – there is usually a better way to write the same … Read more
Read the SICP. Also, there is a PDF Version available.