«

#include <stdio.h>

obj function hello(){
struct obj = { char *data = 'hello'}
obj.add = obj_add(obj);
return obj;
}

void function obj_add(obj){
obj function add(value){
obj.data += value;
return obj;
}
}

void main(){
test = hello();
test.add('world');
printf(test.data);
}

I don't know much c and i was hoping the code above was pointing out
what i am trying to do ?

gert wrote:
> #include <stdio.h>
>
> obj function hello(){
> struct obj = { char *data = 'hello'}
> obj.add = obj_add(obj);
> return obj;
> }
>
> void function obj_add(obj){
> obj function add(value){
> obj.data += value;
> return obj;
> }
> }
>
> void main(){
> test = hello();
> test.add('world');
> printf(test.data);
> }
>
> I don't know much c and i was hoping the code above was pointing out
> what i am trying to do ?
>
You are attempting to write something almost, but not entirely, unlike
C. It is more like JavaScript.

You can't bind functions (or anything else) to structs at runtime in C.

--
Ian Collins.

i started from python actually. I was trying to figure out how to make
a struct that has data and functions defined in the struct it self ?

gert wrote:
> i started from python actually. I was trying to figure out how to make
> a struct that has data and functions defined in the struct it self ?
>
Please keep the context you are replying to.

You can't have functions in structs in C. What yo can have is function
pointers:

struct Obj {
int someInt;
int (*someFn)(void);
};

But you have to assign a function address to the pointer for each
instance of Obj.

--
Ian Collins.

On Feb 9, 1:30 am, Ian Collins <ian-n...@hotmail.com> wrote:
> You can't have functions in structs in C. What yo can have is function
> pointers:
>
> struct Obj {
> int someInt;
> int (*someFn)(void);
>
> };
>
> But you have to assign a function address to the pointer for each
> instance of Obj.

So this means i have to do something like this then ?

#include <stdio.h>

struct obj {
char *data = ''
int (*add)(void);
}

function add(char *value){
obj.data += value;
}

obj function hello(){
obj.data = 'hello';
return obj;
}

void main(){
test = hello();
test.add('world');
printf(test.data);
}

gert wrote:
> On Feb 9, 1:30 am, Ian Collins <ian-n...@hotmail.com> wrote:
>
>>You can't have functions in structs in C. What yo can have is function
>>pointers:
>>
>>struct Obj {
>> int someInt;
>> int (*someFn)(void);
>>
>>};
>>
>>But you have to assign a function address to the pointer for each
>>instance of Obj.
>
>
> So this means i have to do something like this then ?
>
> #include <stdio.h>
>
> struct obj {
> char *data = ''
> int (*add)(void);
> }
>
No, you are still assuming C is an OO language. In C you have to be
explicit:

#include <stdio.h>
#include <stdlib.h>

typedef struct Obj {
int value;
int (*add)(struct Obj*,int);
} Obj;

int add( Obj* obj, int val ) {
obj->value += val;
return obj->value;
}

int main(void) {
Obj* obj = malloc( sizeof obj );

obj->value = 0;
obj->add = add;

obj->add( obj, 42 );

printf( "%d\n", obj->value );

return 0;
}

--
Ian Collins.

Ian Collins wrote:
> int main(void) {
> Obj* obj = malloc( sizeof obj );
>
Oops, malloc( sizeof *obj );


--
Ian Collins.

On 9 Feb, 00:43, "gert" <gert.cuyk...@gmail.com> wrote:
> On Feb 9, 1:30 am, Ian Collins <ian-n...@hotmail.com> wrote:

<snip>


> So this means i have to do something like this then ?

you can't write programs in *any* language by guessing the syntax.
Get a good book (eg. http://cm.bell-labs.com/cm/cs/cbook/index.html).

> #include <stdio.h>
>
> struct obj {
> char *data = ''

string (aka char*) constancts are delimited by " (double quote)
not ' (single quote)

> int (*add)(void);
>
> }
>
> function add(char *value){

C has no keyword "function". A function must return a value.

> obj.data += value;

obj hasn't been defined. Is obj a type or a variable?

>
> }
>
> obj function hello(){
> obj.data = 'hello';
> return obj;
>
> }
>
> void main(){

int main(void)

> test = hello();

test is not defined. This is the wrong syntax for function pointer
assignment.
Or is it a struct assignment? C is strongly typed. You need to decide
on the
type for everything.

> test.add('world');
> printf(test.data);
> }

but the basic problem is you are trying to learn C by guessing.


--
Nick Keighley

gert <> wrote:

> So this means i have to do something like this then ?
> (snip not-C)

No, not really. I've taken the liberty of translating your pseudo-C
into a real C program - which is syntactically correct but *will* fail
(produce undefined behavior) at run time. After considering the vast
differences between your conception of C and what C is, I suggest you
take Mr. Tobin's advice and pick up a C textbook before trying
anything else.

#include <stdio.h>
#include <string.h>

struct obj {
char *data;
void (*add)(struct obj *,char *);
};

void add(struct obj *o, char *value){
strcat(o->data, value); /* assume o->data is large enough */
}

struct obj *hello(struct obj *o){
o->data="hello";
return o;
}

int main(void){
struct obj test;
hello( &test );

test.add=add;
test.add(&test,"world"); /* Syntatically correct but WRONG */
printf("%s\n",test.data);
return 0;
}

--
C. Benson Manica | I *should* know what I'm talking about - if I
cbmanica(at)gmail.com | don't, I need to know. Flames welcome.

On Feb 9, 2:41 am, Ian Collins <ian-n...@hotmail.com> wrote:
> No, you are still assuming C is an OO language. In C you have to be
> explicit:
>
> #include <stdio.h>
> #include <stdlib.h>
>
> typedef struct Obj {
> int value;
> int (*add)(struct Obj*,int);
>
> } Obj;
>
> int add( Obj* obj, int val ) {
> obj->value += val;
> return obj->value;
>
> }
>
> int main(void) {
> Obj* obj = malloc( sizeof obj );
>
> obj->value = 0;
> obj->add = add;
>
> obj->add( obj, 42 );
>
> printf( "%d\n", obj->value );
>
> return 0;
>
> }

Thanks this is exactly what i was guessing for I always start from
this example to learn a language. It defines for me a basic learning
path. So if something doesn't work i have this example to figure out
why a other example doesnt work. I can read about pointers, structs
and functions but that doesnt mean i understand it.

One last sub question, is this a good way to make programs in C by
defining a struct and assign function pointers to it to make it look
like a oo. Or are there other recommended methods to make a program.