Thread: [Dev-C++] structs

Please consider the following code:

1 -#include <stdio.h>
2 -#include <stdlib.h>
3 -
4 -struct car
5 -{
6 -   int size;
7 -   char name[10];
8 -};
9 -
10-int elevator(struct car);
11-
12-int main()
13-{
14-   int floor;
15-   struct car auto;
16-
17-   printf("Enter car name-->");
18-   gets(auto.name);
19-   printf("Enter car size-->");
20-   scanf("%d", &auto.size);
21-   floor = elevator(auto);
22-   printf("Please park your %s in the %d. floor\n", auto.name, floor);
23-   system("PAUSE");
24-   return 0;
25-}
26-
27-int elevator(struct car car_arg)
28-{
29-   if(car_arg.size == 1) return 1;
30-   if(car_arg.size == 2) return 2;
31-   if(car_arg.size == 3) return 3;
32-}

1-I know that I don´t need to pass all the struct. Only the size is enough;
:-)))
2-I know I don´t need the int floor variable. I could directly call the
elevator function as
  argument in line 22 printf; :-)))
3-I am calling the lines 4 until 8, as the "struct definition";
4-I am calling the line 15 and the argument function in line 27, as the
"struct variable
  declarations";

My Questions:
A) My statement in 3 is correct?(y/n, comment)
B) My statement in 4 is correct?(y/n, comment)
C) Is there any way to rewrite this code to avoid a global "struct
definition"? That is, how
   could I eliminate the lines 4 to 8, put them inside main and inside
elevator functions?

Thank you again
Andre

what is the difference between these two

typedef struct _Human
{
   int height;
}Human;

struct Human
{
  int height;
};


and in the first one, what does 'Human' mean at the end? In both structs u 
can declare a Human type, even without the Human thing at the end in the 
first one

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Noorez Kassam wrote:
> what is the difference between these two
>=20
> typedef struct _Human
> {
>   int height;
> }Human;
>=20
> struct Human
> {
>  int height;
> };
>=20
>=20
> and in the first one, what does 'Human' mean at the end? In both struct=
s=20
> u can declare a Human type, even without the Human thing at the end in=20
> the first one

These are the remnants of the C world. The difference is only noticable=20
in C. With the second version in the C world you had to write this to=20
declare a variable (a Human struct):

struct Human MyHuman;

However, with the first one (as Human is a new type in this case), you=20
could write this:

Human MyHuman;

So in the C world, you spared the struct prefix at variable declaration,=20
and saved yourself a lot of typing.

In the C++ world, this is no longer relevant, as struct automatically=20
defines a new type (like class).

--
Greetings,
   Bal=E1zs

In the first one you have declared a struct named _Human and 
instantiated it right after the declaration with name Human. In your 
program you can just say for instance: " Human.height = 1.70 " and it 
will work
Here is another example:
typedef struct _Human {
  int height;
}Human;

int main(){
std::cout << "The Human Project" << std::endl;
std::cout << "How tall are you " ;
std::cin >> Human.height;
return 0;
}

In the second example you have declared a struct named Human, but has 
not yet been instantiated.
Your code would look something like this

struct Human {
 int height;
};
int main(){
Human human; // Instantiating the Human struct
std::cout << "The Human Project" << std::endl;
std::cout << "How tall are you " ;
std::cin >> human.height; // <<==
return 0;
}
Which one is better? it depends on the program you are working on, really!

Hava a good one!
coo...@ho... wrote:

> what is the difference between these two
>
> typedef struct _Human
> {
>   int height;
> }Human;
>
> struct Human
> {
>  int height;
> };
>
>
> and in the first one, what does 'Human' mean at the end? In both 
> structs u can declare a Human type, even without the Human thing at 
> the end in the first one
>
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>
>
>
>
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Maya wrote:
> In the first one you have declared a struct named _Human and=20
> instantiated it right after the declaration with name Human. In your=20
> program you can just say for instance: " Human.height =3D 1.70 " and it=
=20
> will work
> Here is another example:
> typedef struct _Human {
>  int height;
> }Human;
>=20
> int main(){
> std::cout << "The Human Project" << std::endl;
> std::cout << "How tall are you " ;
> std::cin >> Human.height;
> return 0;
> }

No, it is not true. In fact this doesn't even work.

--
Greetings,
   Bal=C3=A1zs

Maya - try compiling your examples :-)

This is a construct that is affected by language.

In C:

struct Human {
...
};

Require you to always declare your variables as:
struct Human a_human;

In C++ - together with the addition of the class keyword - you can get
away with:

struct Human {
...
};

Human a_human;

or
class Human {
public:
...
};

Human a_human;

So basically:

typedef struct Human {
...
} _Human;

declares a structure named Human, and typedef this struct to the name
_Human.

In C, you can then declare a variable as either of:
struct Human a_human; /* referencing the name of the struct */
_Human a_human; /* referencing type typedef name */

while in C++ it doesn't matter. It is even possible to define the data
type as:
typedef struct Human {
..
} Human;
i.e. same name for the struct declaration and for type typedef.

/Per W

On Sat, 31 Jan 2004, Maya wrote:

> In the first one you have declared a struct named _Human and
> instantiated it right after the declaration with name Human. In your
> program you can just say for instance: " Human.height = 1.70 " and it
> will work
> Here is another example:
> typedef struct _Human {
>   int height;
> }Human;
>
> int main(){
> std::cout << "The Human Project" << std::endl;
> std::cout << "How tall are you " ;
> std::cin >> Human.height;
> return 0;
> }
>
> In the second example you have declared a struct named Human, but has
> not yet been instantiated.
> Your code would look something like this
>
> struct Human {
>  int height;
> };
> int main(){
> Human human; // Instantiating the Human struct
> std::cout << "The Human Project" << std::endl;
> std::cout << "How tall are you " ;
> std::cin >> human.height; // <<==
> return 0;
> }
> Which one is better? it depends on the program you are working on, really!
>
> Hava a good one!
> coo...@ho... wrote:
>
> > what is the difference between these two
> >
> > typedef struct _Human
> > {
> >   int height;
> > }Human;
> >
> > struct Human
> > {
> >  int height;
> > };
> >
> >
> > and in the first one, what does 'Human' mean at the end? In both
> > structs u can declare a Human type, even without the Human thing at
> > the end in the first one
> >
> > _________________________________________________________________
> > STOP MORE SPAM with the new MSN 8 and get 2 months FREE*
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> >
> >
> >
> >
> > -------------------------------------------------------
> > The SF.Net email is sponsored by EclipseCon 2004
> > Premiere Conference on Open Tools Development and Integration
> > See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
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>
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>
> FYI
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>
> E-Mail Policy
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>
> * You cannot exercise your power to a point of humiliation.
>                                - Jean Chretien
>
> * The media's the most powerful entity on earth. They have the
>   power to make the innocent guilty and to make the guilty
>   innocent, and that's power.
>                                 - Malcom X
> * "Innocent until proven guilty", no... not in Canada!!
>
>
>
>
> -------------------------------------------------------
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>

Hi,

The former declares a datatype named Human; the latter declares a structure
tag Human. To declare a Human named Joe, in the first case you would simply
type:
Human Joe;

In the latter, it would be:
struct Human Joe;

See also http://www.eskimo.com/~scs/C-faq/q2.1.html

-Ed

 

In the first form you have two different types, and you can use either.

For instance

  struct _Human fred;
  Human joe;
  
Note that it is simply to avoid always having to refer to struct _Human 
that the typedef is used. This is traditional C usage.  

In C++ on the other hand the second form is used, and the type is Human, 
not struct Human.

So you can use 

   Human joe;

C++ compilers will compile the first form too, but the resulting types 
will be _Human and Human unless there is an extern "C" block surrounding 
the declaration.

In article <BAY...@ho...>, 
coo...@ho... (Noorez Kassam) wrote:

> what is the difference between these two
> 
> typedef struct _Human
> {
>    int height;
> }Human;
> 
> struct Human
> {
>   int height;
> };
> 
> 
> and in the first one, what does 'Human' mean at the end? In both 
> structs u can declare a Human type, even without the Human thing at the 
> end in the first one

Please! Foget the auto name!!!! It´s a keyword. Chage it for some like
hot_auto :-)))))
Andre

-----Mensagem original-----
De: André Macário Barros [mailto:and...@su...]
Enviada em: sexta-feira, 11 de abril de 2003 16:09
Para: Dev-Cpp-Users
Assunto: structs


Please consider the following code:

1 -#include <stdio.h>
2 -#include <stdlib.h>
3 -
4 -struct car
5 -{
6 -   int size;
7 -   char name[10];
8 -};
9 -
10-int elevator(struct car);
11-
12-int main()
13-{
14-   int floor;
15-   struct car auto;
16-
17-   printf("Enter car name-->");
18-   gets(auto.name);
19-   printf("Enter car size-->");
20-   scanf("%d", &auto.size);
21-   floor = elevator(auto);
22-   printf("Please park your %s in the %d. floor\n", auto.name, floor);
23-   system("PAUSE");
24-   return 0;
25-}
26-
27-int elevator(struct car car_arg)
28-{
29-   if(car_arg.size == 1) return 1;
30-   if(car_arg.size == 2) return 2;
31-   if(car_arg.size == 3) return 3;
32-}

1-I know that I don´t need to pass all the struct. Only the size is enough;
:-)))
2-I know I don´t need the int floor variable. I could directly call the
elevator function as
  argument in line 22 printf; :-)))
3-I am calling the lines 4 until 8, as the "struct definition";
4-I am calling the line 15 and the argument function in line 27, as the
"struct variable
  declarations";

My Questions:
A) My statement in 3 is correct?(y/n, comment)
B) My statement in 4 is correct?(y/n, comment)
C) Is there any way to rewrite this code to avoid a global "struct
definition"? That is, how
   could I eliminate the lines 4 to 8, put them inside main and inside
elevator functions?

Thank you again
Andre

> -----Original Message-----
> From: dev...@li...
> [mailto:dev...@li...] On Behalf
> Of Andrι Macαrio Barros
> Sent: Friday, April 11, 2003 10:09 PM
> To: Dev-Cpp-Users
> Subject: [Dev-C++] structs
>
>
> Please consider the following code:
>
> 1 -#include <stdio.h>
> 2 -#include <stdlib.h>
> 3 -
> 4 -struct car
> 5 -{
> 6 -   int size;
> 7 -   char name[10];
> 8 -};
> 9 -
> 10-int elevator(struct car);
> 11-
> 12-int main()
> 13-{
> 14-   int floor;
> 15-   struct car auto;
> 16-
> 17-   printf("Enter car name-->");
> 18-   gets(auto.name);
> 19-   printf("Enter car size-->");
> 20-   scanf("%d", &auto.size);
> 21-   floor = elevator(auto);
> 22-   printf("Please park your %s in the %d. floor\n",
> auto.name, floor);
> 23-   system("PAUSE");
> 24-   return 0;
> 25-}
> 26-
> 27-int elevator(struct car car_arg)
> 28-{
> 29-   if(car_arg.size == 1) return 1;
> 30-   if(car_arg.size == 2) return 2;
> 31-   if(car_arg.size == 3) return 3;
> 32-}
>
> 1-I know that I don´t need to pass all the struct. Only the
> size is enough;
> :-)))
> 2-I know I don´t need the int floor variable. I could
> directly call the
> elevator function as
>   argument in line 22 printf; :-)))
> 3-I am calling the lines 4 until 8, as the "struct definition";
> 4-I am calling the line 15 and the argument function in line
> 27, as the
> "struct variable
>   declarations";
>
> My Questions:
> A) My statement in 3 is correct?(y/n, comment)


Yes it is the definition of the struct type.



> B) My statement in 4 is correct?(y/n, comment)


These two are both definitions and declarations. The same way that a
function definition is also a declaration (for example you could have
defined the function at the place where you have the declaration


int elevator(struct car);



> C) Is there any way to rewrite this code to avoid a global "struct
> definition"? That is, how
>    could I eliminate the lines 4 to 8, put them inside main and inside
> elevator functions?


You can't. However keep in mind that a type definition does not occupy
space. Its instances do. That is that only the "auto" object occupies space,
no the definition of struct car.



However the word "auto" is a reserved C keyword (it is the opposite of
keyword "static" for variables), so I do not think that the above would
compile.





Ioannis Vranos

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> -----Original Message-----
> From: dev...@li...=20
> [mailto:dev...@li...] On Behalf=20
> Of Andr? Macario Barros
> Sent: Friday, April 11, 2003 10:09 PM
> To: Dev-Cpp-Users
> Subject: [Dev-C++] structs
>=20
>=20
> Please consider the following code:
>=20
> 1 -#include <stdio.h>
> 2 -#include <stdlib.h>
> 3 -
> 4 -struct car
> 5 -{
> 6 -   int size;
> 7 -   char name[10];
> 8 -};
> 9 -
> 10-int elevator(struct car);
> 11-
> 12-int main()
> 13-{
> 14-   int floor;
> 15-   struct car auto;
> 16-
> 17-   printf("Enter car name-->");
> 18-   gets(auto.name);
> 19-   printf("Enter car size-->");
> 20-   scanf("%d", &auto.size);
> 21-   floor =3D elevator(auto);
> 22-   printf("Please park your %s in the %d. floor\n",=20
> auto.name, floor);
> 23-   system("PAUSE");
> 24-   return 0;
> 25-}
> 26-
> 27-int elevator(struct car car_arg)
> 28-{
> 29-   if(car_arg.size =3D=3D 1) return 1;
> 30-   if(car_arg.size =3D=3D 2) return 2;
> 31-   if(car_arg.size =3D=3D 3) return 3;
> 32-}
>=20
> 1-I know that I don=B4t need to pass all the struct. Only the=20
> size is enough;
> :-)))
> 2-I know I don=B4t need the int floor variable. I could=20
> directly call the
> elevator function as
>   argument in line 22 printf; :-)))
> 3-I am calling the lines 4 until 8, as the "struct definition";
> 4-I am calling the line 15 and the argument function in line=20
> 27, as the
> "struct variable
>   declarations";
>=20
> My Questions:
> A) My statement in 3 is correct?(y/n, comment)


Yes it is the definition of the struct type.



> B) My statement in 4 is correct?(y/n, comment)


These two are both definitions and declarations. The same way that a
function definition is also a declaration (for example you could have
defined the function at the place where you have the declaration


int elevator(struct car);



> C) Is there any way to rewrite this code to avoid a global "struct
> definition"? That is, how
>    could I eliminate the lines 4 to 8, put them inside main and inside
> elevator functions?


You can't. However keep in mind that a type definition does not occupy
space. Its instances do. That is that only the "auto" object occupies =
space,
no the definition of struct car.



However the word "auto" is a reserved C keyword (it is the opposite of
keyword "static" for variables), so I do not think that the above would
compile.





Ioannis Vranos
=20
* Programming pages: http://www.noicys.freeurl.com
* Alternative URL 1: http://run.to/noicys
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