Question

After I’ve seen this PDC session I wanted to try to learn a bit of F#. So I thought the best way would be to rewrite in F# something I’ve already done in C# but my brain just refuses to think in functional mode. I have this abstract class that has some abstract methods and some virtual methods. I would like to override some of virtual methods as well. This class is written in C# and compiled and I don’t intend to rewrite it i F#. So my question is:

1. does anyone have a short sample of how to implement an abstract class, abstract method and virtual method
2. can I have overloaded constructors?
3. are there any constraints if I want to compile it in a dll and make it available to my C# based programs.

Any help would be appreciated.

---

Update: I really really appreciated Brian’s answer but it is still not clear to me so I want to clarify. Let’s pretend this is my abstract class written in C# and compiled in dll. How do I implement it in F#?

public abstract class MyAbstractClass {     public abstract Person GetFullName(string firstName, string lastName);      public abstract bool TryParse(string fullName, out Person person);      public virtual IEnumerable<Person> GetChildren(Person parent)     {         List<Person> kids = new List<Person>();         foreach(Child person in GroupOfPeople)         {             if(person.Parent == parent)                kids.Add(child as Person);         }         return kids;     }      public virtual IEnumerable<Child> GroupOfPeople { get; set; } } 

---

Some documentation for whomever is looking for some F# resources: – if any other F# is interested to get some documentation I found on Don Syme’s (creator of F#) blog free chapters of his book F# Expert. You can download those in doc format.

• Real World Functional Programming by Tomas Petricek has free chapter here

Some other resources that might of interest:

• Scott Hanselman’s blog post
• Dustin Campbell’s blog
• Tomas Petricek’s blog
• The place for F# – hubFS
• F# WIKI
• Microsoft Research

Answer 1

Here’s some sample code

type IBaz =     abstract member Baz : int -> int  [<AbstractClass>] type MyAbsClass() =     // abstract     abstract member Foo : int -> int     // virtual (abstract with default value)     abstract member Bar : string -> int     default this.Bar s = s.Length      // concrete     member this.Qux x = x + 1      // a way to implement an interface     abstract member Baz: int -> int     interface IBaz with         member this.Baz x = this.Baz x  type MySubClass(z : int) =     inherit MyAbsClass()     override this.Foo x = x + 2     override this.Bar s = (base.Bar s) - 1     override this.Baz x = x + 100     member this.Z = z     new () = MySubClass(0)  let c = new MySubClass(42)     printfn '%d %d %d %d %d' c.Z (c.Foo 40) (c.Bar 'two') (c.Qux 41) (c.Baz 42000)