skipping a structure member while initializing

[Mik0b0]

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

[=?utf-8?B?SGFyYWxkIHZhbiBExLNr?=]

Mik0b0 wrote:

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

When a structure has a partial initialiser, the members without an
initialiser get set to 0. You can just as easily type 0 yourself;
there's no difference in effect.

[Mik0b0]

On Mar 10, 2:15 am, "Harald van Dijk" <true...@gmail. comwrote:

Mik0b0 wrote:

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

When a structure has a partial initialiser, the members without an
initialiser get set to 0. You can just as easily type 0 yourself;
there's no difference in effect.

OK, but what can I do if I initialized a2 in every array of structures
before?
I mean

for (i=0;i<2;i++)
{
count[i].a2=(i+1);
};
and after that I want to initialize all other members of all arrays?
Thanks!

[Keith Thompson]

"Mik0b0" <ne****@gmail.c omwrites:

On Mar 10, 2:15 am, "Harald van Dijk" <true...@gmail. comwrote:

>Mik0b0 wrote:

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

When a structure has a partial initialiser, the members without an
initialiser get set to 0. You can just as easily type 0 yourself;
there's no difference in effect.

OK, but what can I do if I initialized a2 in every array of structures
before?
I mean

for (i=0;i<2;i++)
{
count[i].a2=(i+1);
};
and after that I want to initialize all other members of all arrays?

You can only *initialize* an object when you declare it. If you're
executing a for loop that assigns values to the elements of the
arrays, then any initialization is already finished.

C99 does provide compound literals (I've never used them, so I'm not
going to go into any more detail), but there's no way to leave a
"hole" in one. You can assign a compound literal to a struct object,
but by assigning it you're overwriting the entire object.

Can you initialize the object, setting the "skipped" members to 0, and
*then* use a for loop to set values for those members?

--
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."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Matt Kowalczyk]

Mik0b0 wrote:

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

You can try something like this,

#include <stdio.h>

#define NUM(__a) (sizeof(__a) / sizeof((__a)[0]))

struct foo {
int a1;
int a2;
} foobar[10] = {
[0] = {10, 10},
[2] = {20, 2}
};

int main(void) {
int i;

for(i = 0; i < NUM(foobar); i++) {
printf("%d %d\n", foobar[i].a1, foobar[i].a2);
}
return 0;
}
Output:

10 10
0 0
20 2
0 0
0 0
0 0
0 0
0 0
0 0
0 0

This is supported in C99.

-Matt

[Matt Kowalczyk]

Matt Kowalczyk wrote:

Mik0b0 wrote:

>Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

You can try something like this,

#include <stdio.h>

#define NUM(__a) (sizeof(__a) / sizeof((__a)[0]))

struct foo {
int a1;
int a2;
} foobar[10] = {
[0] = {10, 10},
[2] = {20, 2}
};

int main(void) {
int i;

for(i = 0; i < NUM(foobar); i++) {
printf("%d %d\n", foobar[i].a1, foobar[i].a2);
}
return 0;
}
Output:

10 10
0 0
20 2
0 0
0 0
0 0
0 0
0 0
0 0
0 0

This is supported in C99.

-Matt

I read your original question again, and this may also help you,

struct foo {
int a1;
int a2;
} foobar[10] = {
[0].a1 = 10,
[2] = {20, 2}
};

The output would then look something like this,

10 0
0 0
20 2
0 0
0 0
0 0
0 0
0 0
0 0
0 0
-Matt

[SRR]

On Mar 10, 10:00 am, Matt Kowalczyk <matt5...@comca st.netwrote:

Mik0b0 wrote:

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

You can try something like this,

#include <stdio.h>

#define NUM(__a) (sizeof(__a) / sizeof((__a)[0]))

struct foo {
int a1;
int a2;} foobar[10] = {

[0] = {10, 10},
[2] = {20, 2}

};

int main(void) {
int i;

for(i = 0; i < NUM(foobar); i++) {
printf("%d %d\n", foobar[i].a1, foobar[i].a2);
}
return 0;

}

Output:

10 10
0 0
20 2
0 0
0 0
0 0
0 0
0 0
0 0
0 0

I like the code, Its really interesting!

>
This is supported in C99.

Can u tell me where is it mentioned in C99 standards?Pleas e.
Thanks in advance for the reply.

>
-Matt- Hide quoted text -

- Show quoted text -

[santosh]

SRR wrote:

On Mar 10, 10:00 am, Matt Kowalczyk <matt5...@comca st.netwrote:

Mik0b0 wrote:

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

You can try something like this,

#include <stdio.h>

#define NUM(__a) (sizeof(__a) / sizeof((__a)[0]))

struct foo {
int a1;
int a2;} foobar[10] = {

[0] = {10, 10},
[2] = {20, 2}

};

int main(void) {
int i;

for(i = 0; i < NUM(foobar); i++) {
printf("%d %d\n", foobar[i].a1, foobar[i].a2);
}
return 0;

}

[ ... ]

This is supported in C99.

Can u tell me where is it mentioned in C99 standards?Pleas e.
Thanks in advance for the reply.

Section 6.5.2.5 in n1124.pdf - Compound literals.

[CBFalconer]

santosh wrote:

SRR wrote:

.... snip ...

>>
Can u tell me where is it mentioned in C99 standards?Pleas e.
Thanks in advance for the reply.

Section 6.5.2.5 in n1124.pdf - Compound literals.

Your name change to 'u' doesn't appear in the headers.

--
<http://www.cs.auckland .ac.nz/~pgut001/pubs/vista_cost.txt>
<http://www.securityfoc us.com/columnists/423>

"A man who is right every time is not likely to do very much."
-- Francis Crick, co-discover of DNA
"There is nothing more amazing than stupidity in action."
-- Thomas Matthews

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[Rajesh S R]

On Mar 10, 10:23 am, Matt Kowalczyk <matt5...@comca st.netwrote:

Matt Kowalczyk wrote:

Mik0b0 wrote:

Hallo.
Let's say, there is a structure
struct struct10{
int a1;
int a2;
int a3;
int a4;
}count[2]={
{10,20,30,40},
{50,60,70,80}
};

How can I skip a member, e.g. a2 while initializing?
Thanks a lot!

You can try something like this,

#include <stdio.h>

#define NUM(__a) (sizeof(__a) / sizeof((__a)[0]))

struct foo {
int a1;
int a2;
} foobar[10] = {
[0] = {10, 10},
[2] = {20, 2}
};

int main(void) {
int i;

for(i = 0; i < NUM(foobar); i++) {
printf("%d %d\n", foobar[i].a1, foobar[i].a2);
}
return 0;
}

Output:

10 10
0 0
20 2
0 0
0 0
0 0
0 0
0 0
0 0
0 0

This is supported in C99.

-Matt

I read your original question again, and this may also help you,

struct foo {
int a1;
int a2;} foobar[10] = {

[0].a1 = 10,
[2] = {20, 2}

};

The output would then look something like this,

10 0
0 0
20 2
0 0
0 0
0 0
0 0
0 0
0 0
0 0

-Matt- Hide quoted text -

- Show quoted text -

I am not able to understand how the above initialisation is related
with Compound literals though I read about them from Ansi Standards.
Please explain.
Thanks in advance for the reply.