Question

type Foo = 
    class
        inherit Bar

        val _stuff : int

        new (stuff : int) = {
            inherit Bar()
            _stuff = stuff
        }
    end

I want to add this code in above constructor:

if (stuff < 0) then raise (ArgumentOutOfRangeException "Stuff must be positive.")
else ()

How can I achieve this in F# ?

Answer 1

You can do this without needing any workarounds, but the placement of the initial left curly is fairly sensitive (or maybe the parser is buggy?). To do the effect first:

type Foo =
  class
    inherit Bar
    val _stuff : int
    new (stuff : int) = 
      if stuff < 0 then raise (System.ArgumentOutOfRangeException("Stuff must be positive"))
      { 
        inherit Bar() 
        _stuff = stuff 
      }
  end

To do the effect second:

type Foo =
  class
    inherit Bar
    val _stuff : int
    new (stuff : int) = 
      { 
        inherit Bar() 
        _stuff = stuff 
      }
      then if stuff < 0 then raise (System.ArgumentOutOfRangeException("Stuff must be positive"))
  end