dev-cpp-users

[Dev-C++] What are the differences between a struct and a class?

[Andre M. B. <and...@su...>]

Dear users,

   When we need to develop a OO app, one way is to create
classes, with attributes and methods. After this we instanciate
the class in our program, as it is, or with some specialization.

   Thinking only about ANSI-C, we can create structs with the
usual fields (attributes), but we can associate functions inside
the struct too. After this operation, putting this struct definition
in a .h file, we can make a variable declaration defining it as
a struct type (the one created in the .h file).

   In this scenario, disconsidering the protected/public/private
features, please talk to me abou what a OO app can
do that a struct like .c program can´t.

Regards
Andre

Re: [Dev-C++] What are the differences between a struct and a class?

[Derek C. <de...@ci...>]

In C++ the only difference between a struct and a class is that in a
class the default access is private whereas in a struct it is public.
in all other aspects they are the same.

On Fri, Dec 5, 2008 at 12:43 PM, Andre Macario Barros
<and...@su...> wrote:
> Dear users,
>
>    When we need to develop a OO app, one way is to create
> classes, with attributes and methods. After this we instanciate
> the class in our program, as it is, or with some specialization.
>
>    Thinking only about ANSI-C, we can create structs with the
> usual fields (attributes), but we can associate functions inside
> the struct too. After this operation, putting this struct definition
> in a .h file, we can make a variable declaration defining it as
> a struct type (the one created in the .h file).
>
>    In this scenario, disconsidering the protected/public/private
> features, please talk to me abou what a OO app can
> do that a struct like .c program can´t.
>
> Regards
> Andre
>
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Re: [Dev-C++] What are the differences between a struct and a class?

[a.geo <aqu...@gm...>]

This right, the difference is on the logic,... A struct is a organized data
collection... a class is a definition of a live-object, with attributes and
activities (methods).

2008/12/5 Derek Clarke <de...@ci...>

> In C++ the only difference between a struct and a class is that in a
> class the default access is private whereas in a struct it is public.
> in all other aspects they are the same.
>


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Re: [Dev-C++] What are the differences between a struct and a class?

[Chris M. <lor...@gm...>]

On Fri, Dec 5, 2008 at 8:30 AM, Derek Clarke <de...@ci...> wrote:
> In C++ the only difference between a struct and a class is that in a
> class the default access is private whereas in a struct it is public.
> in all other aspects they are the same.

structs are unable to have inheritance if I remember correctly.

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Re: [Dev-C++] What are the differences between a struct and a class?

[Derek C. <de...@ci...>]

On Sat, Dec 6, 2008 at 6:35 AM, Chris Miller
<lor...@gm...> wrote:
> On Fri, Dec 5, 2008 at 8:30 AM, Derek Clarke <de...@ci...> wrote:
>> In C++ the only difference between a struct and a class is that in a
>> class the default access is private whereas in a struct it is public.
>> in all other aspects they are the same.
>
> structs are unable to have inheritance if I remember correctly.
>
On Sat, Dec 6, 2008 at 6:35 AM, Chris Miller
<lor...@gm...> wrote:
> On Fri, Dec 5, 2008 at 8:30 AM, Derek Clarke <de...@ci...> wrote:
>> In C++ the only difference between a struct and a class is that in a
>> class the default access is private whereas in a struct it is public.
>> in all other aspects they are the same.
>
> structs are unable to have inheritance if I remember correctly.

Not true - as I said the *only* difference is the default access.

See below, these were tested on VS2008 Express.

The classes use accessors because the default access is private,
unlike the structs.

Foo.h

#ifndef FOO_H
#define FOO_H

struct Foo
{
       int value;
       Foo() : value(0) {};
       Foo(const int new_value) : value(new_value) {};

       friend ostream& operator<< (ostream& my_stream, const Foo& my_foo);
};

inline ostream& operator<< (ostream& my_stream, const Foo& my_foo)
{
       my_stream << my_foo.value;
       return my_stream;
};


class Foo_class
{
       int value;
public:
       Foo_class() : value(0) {};
       Foo_class (const int new_value) : value(new_value) {};
       const int Value() const { return value;};

       friend ostream& operator<< (ostream& my_stream, const Foo_class& my_foo);
};

inline ostream& operator<< (ostream& my_stream, const Foo_class& my_foo)
{
       my_stream << my_foo.Value();
       return my_stream;
};
#endif /* FOO_H */

Bar.h
#ifndef BAR_H
#define BAR_H

#include "Foo.h"

struct Bar : public Foo
{
       int value2;
       Bar() : value2(0) {};
       Bar(const int new_value) : Foo(0), value2(new_value) {};
       Bar(const int new_value1, const int new_value2) : Foo(new_value1),
value2(new_value2) {};

       friend ostream& operator<< (ostream& my_stream, const Bar& my_bar);
};

inline ostream& operator<< (ostream& my_stream, const Bar& my_bar)
{
       my_stream << my_bar.value << " " << my_bar.value2;
       return my_stream;
};



class Bar_class : public Foo_class
{
       int value2;
public:
       Bar_class() :  value2(0) {};
       Bar_class(const int new_value) : Foo_class(0), value2(new_value) {};
       Bar_class(const int new_value1, int new_value2) :
Foo_class(new_value1), value2(new_value2) {};
       const int Value2() const { return value2; };

       friend ostream& operator<< (ostream& my_stream, const Bar_class& my_bar);
};

inline ostream& operator<< (ostream& my_stream, const Bar_class& my_bar)
{
       my_stream << my_bar.Value() << " " << my_bar.Value2();
       return my_stream;
};

#endif /* BAR_H */

Foobar.cpp
// Foobar.cpp : main project file.

#include "stdafx.h"

#include "Bar.h"


using namespace System;

int main(array<System::String ^> ^args)
{
       Foo foo1(37);
       Foo_class foo2(43);

       Bar bar1(100, 142);
       Bar_class bar2(454, 922);

   cout << "foo1= " << foo1 << endl;
   cout << "foo2= " << foo2 << endl;
   cout << "bar1= " << bar1 << endl;
   cout << "bar2= " << bar2 << endl;

   return 0;
}