general array in C

[Cyn]

Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures in it but what is a good way to be
able to both store pointers to structures and primitive types in it?

[jacob navia]

Cyn wrote:

Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures in it but what is a good way to be
able to both store pointers to structures and primitive types in it?

typedef union {
void *Vptr;
int Int;
short Short;
char Char;
long Long;
long long LLong;
double Double;
long double LDouble;
float Float;
} CELL;

struct ARRAY {
CELL *array;
size_t size;
};

struct ARRAY *newArray(size_ t siz)
{
// Allocates and returns an ARRAY
// ...
}

int main(void)
{
ARRAY *a;

a = newArray(1024);
a.array[23].Float = 2.13f;
a.array[24].Vptr = malloc(267);
a.array[25].LLong = 533777899LL;
a.array[26].Char = 'F';
a.array[27].Vptr = "This is an example string";
}

I would use a type field to avoid mistakes, storing which
type is stored in tha array by changing:
struct ARRAY {
CELL *array;
char *CellTypes;
size_t size;
};

#define VPTR 1
#define INT 2
#define SHORT 3
.... etc

and you store the type of each cell in the adjacent array of characters.
jacob

[Ancient_Hacker]

Cyn wrote:

Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures in it but what is a good way to be
able to both store pointers to structures and primitive types in it?

You're trying to re-invent the C++ object. If you want to do much of
this, it's best to let the C++ compiler and run-time library worry
about all this.

Some other fields you may want to include: the size of each element, a
code for the type of element, the number of dimensions, maybe a link to
the next object (for garbage collection)

[jacob navia]

Ancient_Hacker wrote:

Cyn wrote:

>>Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures in it but what is a good way to be
able to both store pointers to structures and primitive types in it?

You're trying to re-invent the C++ object. If you want to do much of
this, it's best to let the C++ compiler and run-time library worry
about all this.

????

See my post above. Why do you need a "C++ object" to do that?

can you explain?

Thanks

Some other fields you may want to include: the size of each element, a
code for the type of element, the number of dimensions, maybe a link to
the next object (for garbage collection)

[Ancient_Hacker]

jacob navia wrote:

See my post above. Why do you need a "C++ object" to do that?

You don't. And you can build your own jet plane with enough Electrolux
vacuum cleaners, aluminum cat food cans, "crazy glue", and duct tape.
But many people find it easier to just go and buy one off the shelf.

It's just that C++ is really good at doing all the error-prone busywork
of creating objects, and it lets you define operators, often overused,
on those objects.

You can do similar things in C, but the results are rarely pretty,
concise, and easy to use.

Not to polish the C++ apple too much, in many ways it's a horrible
design, but it does do a few things a whole lot better than most of us
can cobble up out of odd bits.

[Frederick Gotham]

Ancient_Hacker posted:

>
Cyn wrote:

>Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures in it but what is a good way
to be able to both store pointers to structures and primitive types in
it?

You're trying to re-invent the C++ object.

Hmm... I don't see how it's anything like a class object in C++. If anything,
I'd say he's trying to implement the Variant type which exists in Visual
Basic.

--

Frederick Gotham

[pete]

Cyn wrote:

>
Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures
in it but what is a good way to be
able to both store pointers to structures and primitive types in it?

With a generic list node:
struct list_node {
struct list_node *next;
void *data;
};
you can have lists of any data format.

--
pete

[jacob navia]

pete wrote:

Cyn wrote:

>>Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures
in it but what is a good way to be
able to both store pointers to structures and primitive types in it?

With a generic list node:
struct list_node {
struct list_node *next;
void *data;
};
you can have lists of any data format.

Yes but if you want to store a character, you waste sizeof(void *) bytes
in a pointer to... 1 byte.

Isn't a union (as I indicated in my answer) a better solution?

[Bart]

Cyn wrote:

Hi,
I want to create a general array structure which can hold all types.
Something like this:

struct ARRAY
{
void **array;
size_t size;
};

Work nice to store pointers to structures in it but what is a good way to be
able to both store pointers to structures and primitive types in it?

If you need dynamic typing why are you using C? A dynamically typed
language such as Scheme or Python would be a better choice for such
things.

Regards,
Bart.

[Bart]

Ancient_Hacker wrote:

Not to polish the C++ apple too much, in many ways it's a horrible
design, but it does do a few things a whole lot better than most of us
can cobble up out of odd bits.

But this case is not that much better suited for C++. See my other
reply for better alternatives.

Regards,
Bart.