Task: Classes

C: #include <stdlib.h>

typedef struct sMyClass
{
  int variable;
} *MyClass;

MyClass  MyClass_new()
{
  MyClass pthis = malloc(sizeof *pthis);
  pthis->variable = 0;
  return pthis;
}

void MyClass_delete(MyClass* pthis)
{
  if (pthis)
  {
    free(*pthis);
    *pthis = NULL;
  }
}

void MyClass_someMethod(MyClass pthis)
{
  pthis->variable = 1;
}

MyClass obj = MyClass_new();
MyClass_someMethod(obj);
MyClass_delete(&obj);










Fortran: 


module accuracy_module
   implicit none
   integer, parameter, public :: rdp = kind(1.d0)
   
   real(rdp), parameter :: pi=3.141592653589793238462643383279502884197_rdp
end module accuracy_module






module typedefs_module
   use accuracy_module
   implicit none

   private 
   public :: TPoint, TShape, TCircle, TRectangle, TSquare 

   
   type, abstract :: TShape
      real(rdp) :: area
      character(len=:),allocatable :: name
   contains
      
      procedure(calculate_area), deferred,pass :: calculate_area
   end type TShape
   
   abstract interface
      function  calculate_area(this)
         use accuracy_module
         import TShape 
         implicit none
         class(TShape) :: this
         real(rdp) :: calculate_area

      end function calculate_area
   end interface

   
   type TPoint
      real(rdp) :: x,y
   end type TPoint

   
   type, extends(TShape) :: TCircle
      real(rdp) :: radius
      real(rdp), private :: diameter
      type(TPoint) :: centre
   contains
      procedure, pass :: calculate_area => calculate_circle_area
      procedure, pass :: get_circle_diameter
      final :: finalize_circle
   end type TCircle

   
   type, extends(TShape) :: TRectangle
      type(TPoint) :: A,B,C,D
   contains
      procedure, pass :: calculate_area => calculate_rectangle_area
      final :: finalize_rectangle
   end type TRectangle

   
   type, extends(TRectangle) :: TSquare
   contains
      procedure, pass :: calculate_area => calculate_square_area
      final :: finalize_square
   end type TSquare

 contains

   
   
   
   subroutine finalize_circle(x)
      type(TCircle), intent(inout) :: x
      write(*,*) "Deleting TCircle object"
   end subroutine finalize_circle

   subroutine finalize_rectangle(x)
      type(TRectangle), intent(inout) :: x
      write(*,*) "Deleting also TRectangle object"
   end subroutine finalize_rectangle

   subroutine finalize_square(x)
      type(TSquare), intent(inout) :: x
      write(*,*) "Deleting TSquare object"
   end subroutine finalize_square

   function calculate_circle_area(this)
      implicit none
      class(TCircle) :: this
      real(rdp) :: calculate_circle_area
      this%area = pi * this%radius**2
      calculate_circle_area = this%area
   end function calculate_circle_area

   function calculate_rectangle_area(this)
      implicit none
      class(TRectangle) :: this
      real(rdp) :: calculate_rectangle_area
      
      this%area = 1
      calculate_rectangle_area = this%area
   end function calculate_rectangle_area

   function calculate_square_area(this)
      implicit none
      class(TSquare) :: this
      real(rdp) :: calculate_square_area
      
      this%area = 1
      calculate_square_area = this%area
   end function calculate_square_area

   function  get_circle_diameter(this)
      implicit none
      class(TCircle) :: this
      real(rdp) :: get_circle_diameter
      this % diameter = 2.0_rdp * this % radius
      get_circle_diameter = this % diameter
   end function get_circle_diameter

end module typedefs_module




program    rosetta_class
   use accuracy_module
   use typedefs_module
   implicit none

   
   call test_types()

 contains

   subroutine test_types()
      implicit none
      
      type(TPoint), target :: point
      
      type(TCircle),target :: circle
      
      type(TSquare),target :: square

      
      class(TPoint), pointer :: ppo
      class(TCircle), pointer :: pci
      class(TSquare), pointer :: psq

      
      point = TPoint(5.d0,5.d0)
      ppo => point
      write(*,*) "x=",point%x,"y=",point%y

      pci => circle

      pci % radius = 1
      write(*,*) pci % radius
      
      write(*,*) pci % get_circle_diameter()
      write(*,*) pci % calculate_area()
      write(*,*) pci % area

      psq => square

      write(*,*) psq % area
      write(*,*) psq % calculate_area()
      write(*,*) psq % area
   end subroutine test_types

end program rosetta_class