Question

I decided to port the class in C# below to F# as an exercise.

It was difficult. I only notice three problems

1) Greet is visible
2) I can not get v to be a static class variable
3) I do not know how to set the greet member in the constructor.

How do i fix these? The code should be similar enough that i do not need to change any C# source. ATM only Test1.v = 21; does not work

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace CsFsTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Test1.hi("stu");
            new Test1().hi();
            Test1.v = 21;
            var a = new Test1("Stan");
            a.hi();
            a.a = 9;

            Console.WriteLine("v = {0} {1} {2}", a.a, a.b, a.NotSTATIC());
        }
    }
    class Test1
    {
        public int a;
        public int b { get { return a * 2; } }
        string greet = "User";
        public static int v;

        public Test1() {}
        public Test1(string name) { greet = name; }

        public static void hi(string greet) { Console.WriteLine("Hi {0}", greet); }
        public void hi() { Console.WriteLine("Hi {0} #{1}", greet, v); }
        public int NotSTATIC() { return v; }
    }
}

F#

namespace CsFsTest

type Test1 = 
    (*
        public int a;
        public int b { get { return a * 2; } }
        string greet = "User";
        public static int v;
    *)
    [<DefaultValue>]
    val mutable a : int
    member x.b = x.a * 2
    member x.greet = "User" (*!! Needs to be private *)

    [<DefaultValue>]
    val mutable v : int (*!! Needs to be static *)

    (*
        public Test1() {}
        public Test1(string name) { greet = name; }
    *)
    new () = {}
    new (name) = { }

    (*  
        public static void hi(string greet) { Console.WriteLine("Hi {0}", greet); }
        public void hi() { Console.WriteLine("Hi {0} #{1}", greet, v); }
        public int NotSTATIC() { return v; }
    *)   
    static member hi(greet) = 
        printfn "hi %s" greet
    member x.hi() =
        printfn "hi %s #%i" x.greet x.v
    member x.NotSTATIC() =
        x.v

Answer 1

Below is some F# that compiles against the C# client.

In .NET, one very rarely exposes public fields; I would recommend against it. The F# syntax for exposing fields is somewhat cumbersome.

namespace CsFsTest

open System

type Test1 =
    val mutable private greet : string
    [<DefaultValue>]
    val mutable public a : int
    [<DefaultValue>]
    static val mutable private vv : int

    static member v with get() = Test1.vv 
                    and set(x) = Test1.vv <- x

    member this.b = this.a*2
    static member hi(greet:string) = Console.WriteLine("Hi {0}", greet)
    member this.hi() = Console.WriteLine("Hi {0} #{1}", this.greet, Test1.v)

    new() = { greet = "User" }
    new(name : string) = { greet = name }

    member this.NotSTATIC() = Test1.v