f#

问题 These languages do not support mutually recursive functions optimization 'natively', so I guess it must be trampoline or.. heh.. rewriting as a loop) Do I miss something? UPDATE: It seems that I did lie about FSharp, but I just didn't see an example of mutual tail-calls while googling 回答1: First of all, F# supports mutually recursive functions natively, because it can benefit from the tailcall instruction that's available in the .NET IL (MSDN). However, this is a bit tricky and may not work

问题 I can do for event in linq.Deltas do or I can do linq.Deltas |> Seq.iter(fun event -> So I'm not sure if that is the same. If that is not the same I want to know the difference. I don't know what to use: iter or for . added - so if that is the matter of choice I prefer to use iter on a top level and for is for closures added some later - looking like iter is map + ignore - it's the way to run from using imperative ignore word. So it's looking like functional way ... 回答1: You can modify

问题 The current state of SIQ was presented by Christopher Vogt at ScalaDays 2011. It was shown how queries would work and look like, but as far as I remember there was no notion about how those types would be represented, e. g. if it is still necessary to write boilerplate code to explain the database structure to Scala. F# 3.0 adds type providers (PDC talk by Don Syme: video; GOTO Copenhagen talk by Tomas Petricek: video, slides, blog post), which make it basically unnecessary to manually write

问题 I wonder what this means in F#. “a function taking an integer, which returns a function which takes an integer and returns an integer.” But I don't understand this well. Can anyone explain this so clear ? [Update]: > let f1 x y = x+y ;; val f1 : int -> int -> int What this mean ? 回答1: F# types Let's begin from the beginning. F# uses the colon ( : ) notation to indicate types of things. Let's say you define a value of type int : let myNumber = 5 F# Interactive will understand that myNumber is

问题 If the pipe operator is created like this: let (|>) f g = g f And used like this: let result = [2;4;6] |> List.map (fun x -> x * x * x) Then what it seems to do is take List.Map and puts it behind (fun x -> x * x * x) And doesn't change anything about the position of [2;4;6] So now it looks like this: let result2 = [2;4;6] (fun x -> x * x * x) List.map However this doesn't work. I am just learning f# for the first time now. And this bothered me while reading a book about f#. So I might learn

问题 I would like to try developing ASP.NET and ASP.NET MVC apps in F# . I enjoy using functional langauges, and to my mind the functional paradigm fits better with HTTP and the web than imperative programming (though of course F# can do both). I am only intending on trying F# for some personal projects, though I hope that eventually F# will be seen as a valid alternative to C# for suitable commercial ASP.NET projects. What pitfalls and rough edges are there currently for using F# with ASP.NET?

问题 I have the very latest version of Visual Studio 2017 installed. I selected F# language support and F# desktop support. After restarting and going to File -> New Project I was expecting to see an option to start a new WPF or WinForms project for F# but I don't have any such options. Only console, library, ASP.NET core, and the tutorial. How can I enable or find the new project templates for F# desktop applications? 回答1: As far as I know, there are no "out of the box" templates for WPF or

问题 In which language is F#'s compiler written? I've heard that F#'s compiler is written in F# :) (each next version of F# compiler is written on its previous version) But: 1. Can't google if it's true. 2. If it's true, in which language is the first version of the F# compiler written? 回答1: The F# compiler is written in F#. The source code is available. It was originally bootstrapped years ago using OCaml, I believe (and perhaps a little C++ as well). (There is still a non-trivial subset of F#

问题 Is there a built-in method to convert the .NET List<> into the F# list? 回答1: Try List.ofSeq in the Microsoft.FSharp.Collections namespace. # List.ofSeq : seq<'T> -> 'T list It's not specifically for System.Collections.Generic.List<T> , but for IEnumerable<T> ( seq<'T> in F#) types in general, so it should still work. (It's also not strictly built into the F# language, but neither is List<T> built into C# or VB.NET. Those are all part of the respective standard libraries.) 回答2: Given

问题 I have this action method in C#: public ActionResult Index() { ViewBag.Message = "Hello"; return View(); } And this view (Index.cshtml): <h2>@ViewBag.Message</h2> And this produces the expected "Hello" on the page. I want to do the controller in F#. I've tried type MainController() = inherit Controller() member x.Index() = x.ViewBag?Message <- "Hello" x.View() And this produces the error message "Method or object constructor 'op_DynamicAssignment' not found". I've looked at some of the F#