Pointers in methods??

[JS]

Is it only allowed to make a pointer point to something in a method??

#include <stdio.h>

struct data {

int x;

int y;

};

struct data test, *pp;

pp = &test; //WHY IS THIS ILLEGAL??
main(){
pp = &test;
}

Why is the above code illegal??

[Mark Odell]

JS wrote:

Is it only allowed to make a pointer point to something in a method??

#include <stdio.h>

struct data {

int x;

int y;

};

struct data test, *pp;

pp = &test; //WHY IS THIS ILLEGAL??
You cannot put run-time code (assignment) outside of a function block.
Do not confuse assignment (run-time) with initialization (compile-time),
e.g.

struct data *pp = &test;


main(){
pp = &test;
This, I trust, works.

}

[Walter Roberson]

In article <d1**********@n ews.net.uni-c.dk>, JS <[e-mail] m> wrote:
:Is it only allowed to make a pointer point to something in a method??

C doesn't have "methods"; from your code I suspect you mean
"functions" .

:struct data { int x; int y; };
:struct data test, *pp;
:pp = &test; //WHY IS THIS ILLEGAL??

Because you have it on a different line, the setting of pp
is not an initializer but rather a statement.

Try

struct data { int x; int y; };
struct data test, *pp = &test;

--
Feep if you love VT-52's.

[Eric Sosman]

JS wrote:

Is it only allowed to make a pointer point to something in a method??

#include <stdio.h>

struct data {

int x;

int y;

};

struct data test, *pp;

pp = &test; //WHY IS THIS ILLEGAL??

Because it is an executable statement, and an executable
statement must reside inside a function (not "method").
This assignment is illegal for the same reason an exit()
call or a `for' loop would be illegal at this point.

However, you can still achieve your goal by using an
initializer in the declaration of `pp':

struct data test, *pp = &test;

or perhaps more clearly

struct data test;
struct data *pp = &test;

Despite the presence of the `=' this is *not* an assignment
statement; it is a declaration with an initializer. Keep in
mind that C tends to re-use the same character for multiple
purposes. Depending on context, `*' can be the multiplication
operator or the pointer dereference operator or part of a `/*'
or `*/' comment marker or part of the `*=' multiply-and-assign
operator. Just so, `=' can be the assignment operator, or part
of the syntax of an initialization, or part of `==' or `!=' or
`*=' or ... Despite the fact that they both use `=' and have
the same set of symbols on both sides of it, your code and mine
are different: one is an executable statement, and the other
is a variable declaration with an initializer.

--
Er*********@sun .com

[Keith Thompson]

"JS" <[e-mail] m> writes:

Is it only allowed to make a pointer point to something in a method??
C has no "methods". It has functions.
#include <stdio.h>

struct data {

int x;

int y;

};

struct data test, *pp;

pp = &test; //WHY IS THIS ILLEGAL??
main(){
pp = &test;
}

Why is the above code illegal??

It's illegal because statements are allowed only within function
bodies.

You can initialize pp if you have an initialization as part of its
declaration:

struct data test, *pp=&test;

or (more clearly IMHO):

struct data test;
struct data *pp = &test;

BTW, indentation makes code easier to read, and you don't need nearly
so many blank lines:

#include <stdio.h>

struct data {
int x;
int y;
};

struct data test;
struct data *pp = &test;

int main(void)
{
pp = &test; /* redundant */
return 0;
}

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Keith Thompson]

Mark Odell <od*******@hotm ail.com> writes:

JS wrote:

Is it only allowed to make a pointer point to something in a method??
#include <stdio.h>
struct data {
int x;
int y;
};
struct data test, *pp;
pp = &test; //WHY IS THIS ILLEGAL??

You cannot put run-time code (assignment) outside of a function
block. Do not confuse assignment (run-time) with initialization
(compile-time), e.g.

struct data *pp = &test;

main(){
pp = &test;

This, I trust, works.

}

Initialization doesn't necessarily happen at compile time, though it
probably does if it's outside a function definition.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Joe Wright]

JS wrote:

Is it only allowed to make a pointer point to something in a method??

#include <stdio.h>

struct data {

int x;

int y;

};

struct data test, *pp;

pp = &test; //WHY IS THIS ILLEGAL??
main(){
pp = &test;
}

Why is the above code illegal??

What's a method?

--
Joe Wright mailto:jo****** **@comcast.net
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[JS]

"Walter Roberson" <ro******@ibd.n rc-cnrc.gc.ca> skrev i en meddelelse
news:d1******** **@canopus.cc.u manitoba.ca...

In article <d1**********@n ews.net.uni-c.dk>, JS <[e-mail] m> wrote:
:Is it only allowed to make a pointer point to something in a method??

C doesn't have "methods"; from your code I suspect you mean
"functions" .

:struct data { int x; int y; };
:struct data test, *pp;
:pp = &test; //WHY IS THIS ILLEGAL??

Because you have it on a different line, the setting of pp
is not an initializer but rather a statement.

Try

struct data { int x; int y; };
struct data test, *pp = &test;

Thats another thing that confuses me why I need to use "," before *pp.
I have made this in my code.

struct data test *pp;

but will only compile if I write:

struct data test, *pp;

[Jens.Toerring]

JS <[e-mail] m> wrote:

"Walter Roberson" <ro******@ibd.n rc-cnrc.gc.ca> skrev i en meddelelse
news:d1******** **@canopus.cc.u manitoba.ca...

In article <d1**********@n ews.net.uni-c.dk>, JS <[e-mail] m> wrote:
:Is it only allowed to make a pointer point to something in a method??

C doesn't have "methods"; from your code I suspect you mean
"functions" .

:struct data { int x; int y; };
:struct data test, *pp;
:pp = &test; //WHY IS THIS ILLEGAL??

Because you have it on a different line, the setting of pp
is not an initializer but rather a statement.

Try

struct data { int x; int y; };
struct data test, *pp = &test;

Thats another thing that confuses me why I need to use "," before *pp.
I have made this in my code. struct data test *pp; but will only compile if I write: struct data test, *pp;

Of course, because you defined _two_ variables, 'test' and 'pp' - and
then you need a comma in between the two. That's the same as with

int i, j;

Leaving out the comma is a syntax error.

Regards, Jens
--
\ Jens Thoms Toerring ___ Je***********@p hysik.fu-berlin.de
\______________ ____________ http://www.toerring.de

[Tor Rustad]

"Keith Thompson" <ks***@mib.or g> wrote in message

<snip>

#include <stdio.h>

struct data {
int x;
int y;
};

struct data test;
struct data *pp = &test;

int main(void)
{
pp = &test; /* redundant */
return 0;
}

This makes "test" and "*pp" global variables. It's better style
to use local variables, since this hide these identifiers from
other functions:

int main (void)
{
struct data test, *pp; /* <--- local to function main */

pp = &test;

return 0;
}

I once asked an expert COBOL programmer, how to
declare local variables in COBOL, the reply was:
"what is a local variable?"

--
Tor <torust AT online DOT no>