Re: Translating C++ class types into Ada tagged types?

[markus034@gmail.com]

On Jul 9, 7:12 pm, "jimmaureenrog...@worldnet.att.net"
<jimmaureenrog...@worldnet.att.net> wrote:
> On Jul 9, 7:39 pm, markus...@gmail.com wrote:
>
>
>
> > Does ada fully support the object-orientedness? If so, how do i write
> > (or translate) the following C++ object-oriented code into Ada object-
> > oriented code?
> > Without constractors:
> > 1:   // Demonstrates declaration of a class and
> > 2:   // definition of class methods,
> > 3:
> > 4:   #include <iostream.h>      // for cout
> > 5:
> > 6:   class Cat                   // begin declaration of the class
> > 7:   {
> > 8:     public:                   // begin public section
> > 9:       int GetAge();           // accessor function
> > 10:      void SetAge (int age);  // accessor function
> > 11:      void Meow();            // general function
> > 12:    private:                  // begin private section
> > 13:      int itsAge;             // member variable
> > 14:  };
> > 15:
> > 16:  // GetAge, Public accessor function
> > 17:  // returns value of itsAge member
> > 18:  int Cat::GetAge()
> > 19:  {
> > 20:     return itsAge;
> > 21:  }
> > 22:
> > 23:  // definition of SetAge, public
> > 24:  // accessor function
> > 25:  // returns sets itsAge member
> > 26:  void Cat::SetAge(int age)
> > 27:  {
> > 28:     // set member variable its age to
> > 29:     // value passed in by parameter age
> > 30:     itsAge = age;
> > 31:  }
> > 32:
> > 33:  // definition of Meow method
> > 34:  // returns: void
> > 35:  // parameters: None
> > 36:  // action: Prints "meow" to screen
> > 37:  void Cat::Meow()
> > 38:  {
> > 39:     cout << "Meow.\n";
> > 40:  }
> > 41:
> > 42:  // create a cat, set its age, have it
> > 43:  // meow, tell us its age, then meow again.
> > 44:  int main()
> > 45:  {
> > 46:     Cat Frisky;
> > 47:     Frisky.SetAge(5);
> > 48:     Frisky.Meow();
> > 49:     cout << "Frisky is a cat who is " ;
> > 50:     cout << Frisky.GetAge() << " years old.\n";
> > 51:     Frisky.Meow();
> > 52;      return 0;
> > 53: }
> > Also the same code with constractors:
> > 1:   // Demonstrates declaration of a constructors and
> > 2:   // destructor for the Cat class
> > 3:
> > 4:   #include <iostream.h>      // for cout
> > 5:
> > 6:   class Cat                   // begin declaration of the class
> > 7:   {
> > 8:    public:                    // begin public section
> > 9:      Cat(int initialAge);     // constructor
> > 10:     ~Cat();                  // destructor
> > 11:     int GetAge();            // accessor function
> > 12:     void SetAge(int age);    // accessor function
> > 13:     void Meow();
> > 14:   private:                   // begin private section
> > 15:     int itsAge;              // member variable
> > 16:  };
> > 17:
> > 18:  // constructor of Cat,
> > 19:  Cat::Cat(int initialAge)
> > 20:  {
> > 21:     itsAge = initialAge;
> > 22:  }
> > 23:
> > 24:  Cat::~Cat()                 // destructor, takes no action
> > 25:  {
> > 26:  }
> > 27:
> > 28:  // GetAge, Public accessor function
> > 29:  // returns value of itsAge member
> > 30:  int Cat::GetAge()
> > 31:  {
> > 32:     return itsAge;
> > 33:  }
> > 34:
> > 35:  // Definition of SetAge, public
> > 36:  // accessor function
> > 37:
> > 38:  void Cat::SetAge(int age)
> > 39:  {
> > 40:     // set member variable its age to
> > 41:     // value passed in by parameter age
> > 42:     itsAge = age;
> > 43:  }
> > 44:
> > 45:  // definition of Meow method
> > 46:  // returns: void
> > 47:  // parameters: None
> > 48:  // action: Prints "meow" to screen
> > 49:  void Cat::Meow()
> > 50:  {
> > 51:     cout << "Meow.\n";
> > 52:  }
> > 53:
> > 54:  // create a cat, set its age, have it
> > 55   // meow, tell us its age, then meow again.
> > 56:  int main()
> > 57:  {
> > 58:    Cat Frisky(5);
> > 59:    Frisky.Meow();
> > 60:    cout << "Frisky is a cat who is " ;
> > 61:    cout << Frisky.GetAge() << " years old.\n";
> > 62:    Frisky.Meow();
> > 63:    Frisky.SetAge(7);
> > 64:    cout << "Now Frisky is " ;
> > 65:    cout << Frisky.GetAge() << " years old.\n";
> > 66;     return 0;
> > 67: }
>
> Ada is object oriented, but does not provide constructors or
> destructors. The following code is similar to your example
> without constructors or destructors.
>
> Ada uses packages for encapsulation. The following package defines
> a Cat tagged type and three methods for that type. The package
> specification
> provides all interface definitions for Cat.
>
> package Animals is
>    type Cat is tagged private;
>    function Get_Age(Fluffy : Cat) return Positive;
>    procedure Set_Age(The_Cat : in out Cat; Age : in Positive);
>    procedure Meow(The_Cat : Cat);
> private
>    type Cat is tagged record
>       Age : Positive;
>    end record;
> end Animals;
>
> with Ada.Text_Io;
>
> The following package body contains the implementation of the
> function and two procedures.
>
> package body Animals is
>
>    -------------
>    -- Get_Age --
>    -------------
>
>    function Get_Age (Fluffy : Cat) return Positive is
>    begin
>       return Fluffy.Age;
>    end Get_Age;
>
>    -------------
>    -- Set_Age --
>    -------------
>
>    procedure Set_Age (The_Cat : in out Cat; Age : in Positive) is
>    begin
>       The_Cat.Age := Age;
>    end Set_Age;
>
>    ----------
>    -- Meow --
>    ----------
>
>    procedure Meow(The_Cat : Cat) is
>    begin
>       Ada.Text_IO.Put_Line("Meow.");
>    end Meow;
>
> end Animals;
>
> Finally, here is the entry point procedure equivalent to the C++
> main function.
>
> with Animals;
> use type Animals.Cat;
> with Ada.Text_Io;
>
> procedure Cat_Main is
>    Frisky : Animals.Cat;
> begin
>    Frisky.Set_Age(5);
>    Frisky.Meow;
>    Ada.Text_Io.Put("Frisky is a cat who is");
>    Ada.Text_Io.Put_Line(Positive'Image(Frisky.Get_Age) & " years
> old.");
> end Cat_Main;
>
> Jim Rogers

The code you translated works perfectly. I've been thinking on how to
translate that code for about two weeks and i couldn't figure it out.
Now i begin to understand how object-orientation works in ada.
Jim Rogers, I really appreciate your help.
Thanks a lot.