why can not assign value to an array variable of a structure?

[baumann@pan]

hi all,


#include "stdafx.h"

struct a_{
int a;
int b;
};

struct a_ a1 ,a2, a3, a4, a5, a6;
#if 0
struct a_ m[6] = { a1,a2,a3,a4,a5,a6};
#endif
int a[6] = { 1, 2, 3, 4, 5, 6};

int main(int argc, char* argv[])
{
printf("Hello World!\n");
return 0;
}


the above code tells me struct a_ m[6] ={ }; statement is wrong,

but why int a[6] ={}; is ok?

i know if i write struct a_ m[6] = {
{a1.a,a1.b},{a2.a,a2.b},{a3.a,a3.b},{
a4.a,a4.b},{a5.a,a5.b}}; it will be ok, i have not test the idea.

 

[Arun]

struct a_ m[6] = { a1,a2,a3,a4,a5,a6};

initialization elements must be constants which in this case (a1..a6)
are not.

-ASJ

 

[Chris \( Val \)]

| hi all,
|
|
| #include "stdafx.h"
|
| struct a_{
| int a;
| int b;
| };
|
| struct a_ a1 ,a2, a3, a4, a5, a6;
| #if 0
| struct a_ m[6] = { a1,a2,a3,a4,a5,a6};
| #endif
| int a[6] = { 1, 2, 3, 4, 5, 6};
|
| int main(int argc, char* argv[])
| {
| printf("Hello World!\n");
| return 0;
| }
|
|
| the above code tells me struct a_ m[6] ={ }; statement is wrong,
|
| but why int a[6] ={}; is ok?

It might be a compiler bug?
It works fine with MinGW.

| i know if i write struct a_ m[6] = {
| {a1.a,a1.b},{a2.a,a2.b},{a3.a,a3.b},{
| a4.a,a4.b},{a5.a,a5.b}}; it will be ok, i have not test the idea.

The following should work:
a_ m[6] = { {5,10}, {15,20}, {25,30}, {35,40}, {45,50}, {55,60} };

Btw, you don't need the 'struct' keyword in the declaration
in C++.

Cheers,
Chris Val

 

[John Carson]

hi all,


#include "stdafx.h"

struct a_{
int a;
int b;
};

struct a_ a1 ,a2, a3, a4, a5, a6;
#if 0
struct a_ m[6] = { a1,a2,a3,a4,a5,a6};
#endif
int a[6] = { 1, 2, 3, 4, 5, 6};

int main(int argc, char* argv[])
{
printf("Hello World!\n");
return 0;
}


the above code tells me struct a_ m[6] ={ }; statement is wrong,

but why int a[6] ={}; is ok?

i know if i write struct a_ m[6] = {
{a1.a,a1.b},{a2.a,a2.b},{a3.a,a3.b},{
a4.a,a4.b},{a5.a,a5.b}}; it will be ok, i have not test the idea.

It compiles without complaint on VC++ 7.1 and Comeau.

 

[baumann@pan]

i am using VC++ 6, not the one u use.

does the standard of C99 /C++ guide what we should do under this case?

 

[baumann@pan]

i tried with vs.net 2003 studio, it works, but VC++ 6.0 really fails to
compile the code.

 

[Jack Klein]

i am using VC++ 6, not the one u use.

does the standard of C99 /C++ guide what we should do under this case?

The standard of C99 is not relevant to C++. The C++ standard is based
in part on the C standard as of 1995.

As for the C++ standard, it suggests that you use a compiler that
conforms to the C++ standard. Microsoft Visual C++ 6.0 does not.

 

[baumann@pan]

The standard of C99 is not relevant to C++. The C++ standard is based
in part on the C standard as of 1995.

As for the C++ standard, it suggests that you use a compiler that
conforms to the C++ standard. Microsoft Visual C++ 6.0 does not.

according to your view, if the compiler conforms to the C++ standard,
the code should work? right? thanks

 

[Achintya]

Hi,

As mentioned by Mr. Arun also, this kind of array initialization
requires constant values.
Since the struct are already initialized to zero( static variable
initilization) in the previous statement i.e

struct a_ a1 ,a2, a3, a4, a5, a6;

...those values are considered for initialization in the array of
structs if you use...

struct a_ m[6] =
{{a1.a,a1.b},{a2.a,a2.b},{a3.a,a3.b},{a4.a,a4.b},{a5.a,a5.b}};

....and if you use....

a_ m[6] = {10,20,30,40,50,60};

....the initialization is m[0].a=10, m[0].b=20,
m[1].a=30....m[4].a=0...etc...

I have tried on VC++ 6.0.