Two ways of defining classes in F#

While reading documentation about F# I learned about two ways for defining classes.

In F# you have several options for defining data structures including records, discriminated unions and classes . A nice resource for learning about the syntax of class definitions is Object Model Syntax Examples also F# Overview (III.) - Imperative and Object-Oriented Programming and the F# Manual: Class definitions provide more information.

The first way of defining classes defines the object construction parts explicitly:

type Shape = class
   val x : int
   val y : int
   
   new(aX,aY) =
     { x = aX ;
       y = aY }
 
   override self.ToString() =
        string.Format("({0},{1})",self.x, self.y)
     
end

type Square = class
   inherit Shape as baseClass
   val side : int
   
   new (aX,aY,aSide) = {
      inherit Shape(aX,aY) ;
      side = aSide
   }
   
   override self.ToString() =
     string.Format("{0} -- {1}",baseClass.ToString(), self.side)
end

The second way uses implicit construction:

type Shape(x : int,y : int) = class 
   override self.ToString() =
        string.Format("({0},{1})",x, y)
     
end

type Square(x : int,y : int,side : int) = class
   inherit Shape(x,y) as baseClass
     
   override self.ToString() =
     string.Format("{0} -- {1}",baseClass.ToString(), side)

end