enum-type anonymous structs

[andreyvul]

If I try compiling this in gcc, it says: "error: request for member
`baz' in something not a structure or union".
Any workarounds or tips on how to make a structure such that it
behaves like an enum but its members can be addressed with '.'?
I don't want to have to do this using #defines, as it would be far too
messy.
code:
static struct {
static const int baz = 1;
} bar;

void foo() {
int x = bar.baz;
}

[Ravishankar S]

"andreyvul" <an********@gma il.comwrote in message
news:b2******** *************** ***********@q77 g2000hsh.google groups.com...

On Jan 2, 8:48 pm, Dan Henry <use...@danlhen ry.comwrote:

How does the functionality of enums and structures intersect?

enums are lists of constants, correct?
What if the list could be accessed using struct format, like
enum.member?

enums are something like compile time constants in C. But it does not
introduce a
namespace. For example the folowing code gave me errors..

#include <stdio.h>

enum RainBColor {
VIOLET = 0,
INDIGO = 1,
BLUE = 2,
..

};
enum Color {
WHITE = 0;
BLUE = 1;

};
int main(void)
{
enum Color color = BLUE;
printf("color has the integer value = %d\n",(int)colo r);
return 0;
}

color.c:12: error: conflicting types for `BLUE'
color.c:7: error: previous declaration of `BLUE'

Only way out in C is to use a prefix like RB_BLUE and COL_BLUE. Sure it
would be nice if C had let us
refer the enum consts in someways like

1) Color.BLUE,Rain BColor.BLUE // I think PASCAL has this method.
2) Color::BLUE and RainBColor::Blu e

It would sure make for readability as clarity.

Suppose we use const structs, we lose the "type info" since we have to refer
to the variable as plain "ints".

typedef const struct {
unsigned char WHITE = 0;
unsigned char BLUE = 1;
..
} Color;

typedef const struct {
unsigned char VIOLET = 0;
unsigned charu INDIGO = 1;
unsigned char BLUE = 2;
..
};

int main(void)
{
unsigned char color = RainBColor.BLUE ; /* But type is now "unsigned
char" */

}

[Ravishankar S]

"Ravishanka r S" <ra***********@ in.bosch.comwro te in message
news:fl******** **@news4.fe.int ernet.bosch.com ...

"andreyvul" <an********@gma il.comwrote in message
news:b2******** *************** ***********@q77 g2000hsh.google groups.com...

On Jan 2, 8:48 pm, Dan Henry <use...@danlhen ry.comwrote:

How does the functionality of enums and structures intersect?

enums are lists of constants, correct?
What if the list could be accessed using struct format, like
enum.member?

enums are something like compile time constants in C. But it does not
introduce a
namespace. For example the folowing code gave me errors..

#include <stdio.h>

enum RainBColor {
VIOLET = 0,
INDIGO = 1,
BLUE = 2,
..

};
enum Color {
WHITE = 0;
BLUE = 1;

};
int main(void)
{
enum Color color = BLUE;
printf("color has the integer value = %d\n",(int)colo r);
return 0;
}

color.c:12: error: conflicting types for `BLUE'
color.c:7: error: previous declaration of `BLUE'

Only way out in C is to use a prefix like RB_BLUE and COL_BLUE. Sure it
would be nice if C had let us
refer the enum consts in someways like

1) Color.BLUE,Rain BColor.BLUE // I think PASCAL has this method.
2) Color::BLUE and RainBColor::Blu e

It would sure make for readability and clarity.

Suppose we use const structs, we lose the "type info" since we have to

refer

to the variable as plain "ints". It also involves memory for the const

structs..

>
const struct {
unsigned char WHITE = 0;
unsigned char BLUE = 1;
..
} Color;

const struct {
unsigned char VIOLET = 0;
unsigned char INDIGO = 1;
unsigned char BLUE = 2;
..
}RainBColor;

int main(void)
{
unsigned char color = RainBColor.BLUE ; /* But type is now "unsigned
char" */

}

[Martin Ambuhl]

andreyvul wrote:

If I try compiling this in gcc, it says: "error: request for member
`baz' in something not a structure or union".

That's strange. My copy of gcc gives a number of messages. See below.

Any workarounds or tips on how to make a structure such that it
behaves like an enum but its members can be addressed with '.'?

structs are not enums. It doesn't even make sense for them to "behave
like an enum."

>

static struct {
static const int baz = 1;
} bar;

void foo() {
int x = bar.baz;
}

Notice the diagnostics gcc gives me for your code:
3: error: expected specifier-qualifier-list before 'static'
4: warning: struct has no members
In function 'foo':
8: error: 'struct <anonymous>' has no member named 'baz'
8: warning: unused variable 'x'

These arise because there is no such thing as a static member in a C
struct. Perhaps you wanted to use some other language.

[andreyvul]

On Jan 3, 2:12 am, Martin Ambuhl <mamb...@earthl ink.netwrote:

andreyvul wrote:

If I try compiling this in gcc, it says: "error: request for member
`baz' in something not a structure or union".

That's strange. My copy of gcc gives a number of messages. See below.

Any workarounds or tips on how to make a structure such that it
behaves like an enum but its members can be addressed with '.'?

structs are not enums. It doesn't even make sense for them to "behave
like an enum."

>
>

static struct {
static const int baz = 1;
} bar;

void foo() {
int x = bar.baz;
}

Notice the diagnostics gcc gives me for your code:
3: error: expected specifier-qualifier-list before 'static'
4: warning: struct has no members
In function 'foo':
8: error: 'struct <anonymous>' has no member named 'baz'
8: warning: unused variable 'x'

These arise because there is no such thing as a static member in a C
struct. Perhaps you wanted to use some other language.

I used structs so that I could namespace constants, namely error
codes.

[andreyvul]

On Jan 2, 11:50 pm, Jack Klein <jackkl...@spam cop.netwrote:

On Wed, 2 Jan 2008 16:12:14 -0800 (PST), andreyvul
<andrey....@gma il.comwrote in comp.lang.c:

If I try compiling this in gcc, it says: "error: request for member
`baz' in something not a structure or union".
Any workarounds or tips on how to make a structure such that it
behaves like an enum but its members can be addressed with '.'?
I don't want to have to do this using #defines, as it would be far too
messy.
code:
static struct {
static const int baz = 1;
} bar;

void foo() {
int x = bar.baz;
}

A few others have questioned why you want to do it, but I haven't seen
anyone post a suggestion like this:

struct bar { int baz; };

static const struct bar bar = { 1 };

void foo(void)
{
int x = bar.baz;

}

You just need to define the type, and than a const initialized (and
static, if you want) object of the type separately.

Fails if you do this:
void foo(int x) {
switch (x) {
case bar.baz:
...
}
}

[andreyvul]

On Jan 3, 12:46 pm, andreyvul <andrey....@gma il.comwrote:

I used structs so that I could namespace constants, namely error
codes.

To use as cases in a switch(setjmp(b uf)) statement.

[Chris Dollin]

andreyvul wrote:

I used structs so that I could namespace constants, namely error
codes.

It has presumably become apparent to you that you can't do
this in C; you're essentially stuck with naming conventions.
Just pick good names and wash thoroughly and you'll be OK.

--
Preprocessor Hedgehog
"Who do you serve, and who do you trust?" /Crusade/