dev-cpp-users

[Dev-C++] What's the difference?

[Robson B. <rob...@su...>]

Hi coders,

what's the difference between using pointers and using simple variables? How
does this difference affects the performance of my code? I know that using
pointers is working with memory addresses but using simple variables would
not have the same effect?

int *number or int number: what's the best to be used?


Thanks!

Re: [Dev-C++] What's the difference?

[<st...@xs...>]

This really depends on what you're doing.  The main benefit to pointers is that 
you can send them to functions where the function can modify the value of that 
pointer variable.  With normal variables they only get passed by value and 
since you can only have one return value per function it sometimes becomes 
necessary to modify the variables within your function rather than calling the 
funtion multiple times or writing multiple functions that return slightly 
different variables.

Thanks,
Steven

Quoting Robson Bernard <rob...@su...>:

> Hi coders,
> 
> what's the difference between using pointers and using simple variables? How
> does this difference affects the performance of my code? I know that using
> pointers is working with memory addresses but using simple variables would
> not have the same effect?
> 
> int *number or int number: what's the best to be used?
> 
> 
> Thanks!
> 
> 
> 
> -------------------------------------------------------
> This sf.net email is sponsored by:ThinkGeek
> Welcome to geek heaven.
> http://thinkgeek.com/sf
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> Dev-cpp-users mailing list
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> 

Re: [Dev-C++] What's the difference?

[Adam M. <up...@in...>]

Hi.

If you don't need pointers - don't use them. Unfortunately sometimes it is
indispensable to use pointers. One little and simple example:
when you want to pass argument to function and this function
chages its value. To do this you must pass pointer or reference to
the argument. And one more usage of pointers - dynamic memory
allocation.

regards
Adam

> Hi coders,
>
> what's the difference between using pointers and using simple variables?
How
> does this difference affects the performance of my code? I know that using
> pointers is working with memory addresses but using simple variables would
> not have the same effect?
>
> int *number or int number: what's the best to be used?
>
>
> Thanks!


----------------------------------------------------------------------
KLIKAJ!!! Nie pytaj dlaczego... >>> http://link.interia.pl/f16e2

Re: [Dev-C++] What's the difference?

[<or...@vp...>]

Hello!

> what's the difference between using pointers and using simple variables? How
> does this difference affects the performance of my code? I know that using
> pointers is working with memory addresses but using simple variables would
> not have the same effect?
It is advisable to use pointers when you use structures, because it is 
faster and more convenient. Suppose you have this structure:
struct foo{
   char *Text1;
   char *Text2;
   char *Text3;
};

If you have a function that has this structure as its argument, then it 
is better to pass only a pointer to it (&foo_struct), beacuse it already 
has pointers in it to character arrays, so you have the same result if 
you pass pointer or pass the whole struct. But when passing the whole 
struct, it will be copied, but the Texts won't, just the pointers to it. 
So it is better to pass only pointers to structs, always. It will make 
your code cleaner, and you can always assure yourself, that you always 
declared functions to use pointers.

--
Greetings,
   Balázs

Re: [Dev-C++] What's the difference?

[Ioannis V. <no...@ho...>]

-------Original Message-------=0D
 =0D
From: OROSZI Bal=E1zs=0D
Date: =D4=F1=DF=F4=E7, 4 =CC=DC=F1=F4=E9=EF=F2 2003 12:29:50 =F0=EC=0D
To: dev...@li...=0D
Subject: Re: [Dev-C++] What's the difference?=0D
 =0D
Hello!=0D
=0D
It is advisable to use pointers when you use structures, because it is =0D
faster and more convenient. Suppose you have this structure:=0D
struct foo{=0D
char *Text1;=0D
char *Text2;=0D
char *Text3;=0D
};=0D
=0D
If you have a function that has this structure as its argument, then it =0D
is better to pass only a pointer to it (&foo_struct), beacuse it already =
=0D
has pointers in it to character arrays, so you have the same result if =0D
you pass pointer or pass the whole struct. But when passing the whole =0D
struct, it will be copied, but the Texts won't, just the pointers to it. =
=0D
So it is better to pass only pointers to structs, always. It will make =0D
your code cleaner, and you can always assure yourself, that you always =0D
declared functions to use pointers.=0D
=0D
=0D
=3D=3D> ? In fact allocating/releasing space on the free store is more
time-expensive than using local space in the stack. So for example:=0D
=0D
// C++=0D
=0D
struct foo=0D
{=0D
 char *Text1, *Text2, *Text3;=0D
};=0D
=0D
=0D
foo something;=0D
=0D
something.Text1=3Dnew char[20];=0D
something.Text2=3Dnew char[30];=0D
something.Text3=3Dnew char[40];=0D
=0D
// ...=0D
=0D
delete [] something.Text1;=0D
delete [] something.Text2;=0D
delete [] something.Text3;=0D
=0D
=0D
is more than expensive than=0D
=0D
=0D
struct foo=0D
{=0D
 char Text1[20], Text2[30], Text3[40];=0D
};=0D
=0D
foo something;=0D
=0D
=0D
// "something" dies at the end of its scope=0D
=0D
=0D
=3D=3D> Not to mention allocating something itself on the free store.=0D
=0D
=3D=3D> Passing a pointer to struct with local arrays doesn't copy anythi=
ng
except of the pointer address (value). For example:=0D
=0D
=0D
struct foo=0D
{=0D
 char text1[10], text2[20], text3[30];=0D
};=0D
=0D
=0D
=0D
void whatever(foo *);=0D
=0D
=0D
int main()=0D
{=0D
 foo something=3D{"telos", "ton", "imeron"};=0D
=0D
 whatever(&something);=0D
=0D
}=0D
=0D
=0D
// Passed by "reference".=0D
// Only the address of something is copied, not its elements.=0D
void whatever(foo *pf)=0D
{=0D
 // ...=0D
}=0D
=0D
=0D
=0D
=3D=3D> However i do not like this style. How i would do it:=0D
=0D
#include <string>=0D
=0D
struct foo=0D
{=0D
 std::string text1, text2, text3;=0D
=0D
 foo(const std::string &t1, const std::string &t2, const std::string &t3)=
:=0D
     text1(t1), text2(t2), text3(t3) { }=0D
=0D
};=0D
=0D
=0D
=0D
void whatever(foo &);=0D
=0D
=0D
int main()=0D
{=0D
 foo something("telos", "ton", "imeron");=0D
=0D
 whatever(something);=0D
=0D
}=0D
=0D
void whatever(foo &pf)=0D
{=0D
 // ...=0D
}=0D
=0D
=0D
=0D
=3D=3D> Or even better i would provide it as a class with access function=
s.=0D
=0D
=0D
=0D
Ioannis Vranos=0D
=0D
* Programming pages: http://www.noicys.freeurl.com=0D
* Alternative URL: http://run.to/noicys=20

Re: [Dev-C++] What's the difference?

[<or...@vp...>]

Ioannis Vranos wrote:
> ==> ? In fact allocating/releasing space on the free store is more 
> time-expensive than using local space in the stack.
It is, but using the stack is only advisable for temporary structures.

> How i would do it:
>  
> #include <string>
>  
> struct foo
> {
>  std::string text1, text2, text3;
>  
>  foo(const std::string &t1, const std::string &t2, const std::string &t3):
>      text1(t1), text2(t2), text3(t3) { }
>  
> };
>  
> void whatever(foo &);
> int main()
> {
>  foo something("telos", "ton", "imeron");
>  whatever(something);
> }
>  
> void whatever(foo &pf)
> {
>  // ...
> }
>  
> ==> Or even better i would provide it as a class with access functions.
Well yes, I see now. I don't know C++, so I looked up in a book what you 
wrote, and it seems you use references. Isn't that the same as using 
pointers?
Anyway, in C, pointers are the only way.

--
Greetings,
   Balázs

Re: [Dev-C++] What's the difference?

[Ioannis V. <no...@ho...>]

-------Original Message-------=0D
 =0D
From: OROSZI Bal=E1zs=0D
Date: =D4=F1=DF=F4=E7, 4 =CC=DC=F1=F4=E9=EF=F2 2003 5:34:24 =EC=EC=0D
To: dev...@li...=0D
Subject: Re: [Dev-C++] What's the difference?=0D
 =0D
Ioannis Vranos wrote:=0D
> =3D=3D> ? In fact allocating/releasing space on the free store is more =
=0D
> time-expensive than using local space in the stack.=0D
=0D
It is, but using the stack is only advisable for temporary structures.=0D
=0D
=0D
=3D=3D> Well it depends. You can use the stack to callers and pass the st=
ack
entities to called functions.=0D
=0D
=0D
=0D
=0D
=0D
=0D
>> =0D
> =3D=3D> Or even better i would provide it as a class with access functi=
ons.=0D
=0D
Well yes, I see now. I don't know C++, so I looked up in a book what you =
=0D
wrote, and it seems you use references. Isn't that the same as using =0D
pointers?=0D
Anyway, in C, pointers are the only way.=0D
=0D
=0D
Yes. I did not know what language was all about and i assumed C++.=0D
=0D
=0D
Ioannis Vranos=0D
=0D
* Programming pages: http://www.noicys.freeurl.com=0D
* Alternative URL: http://run.to/noicys=20