psuedo-class

[chrismiceli]

Is there a way to imitate a class in c, I know something like this will work

#include <stdio.h>

int main(void) {
     struct character {
          int (*print_char)(int num);
     };
 
     struct character my_character;
     my_character.print_char = putchar;
     my_character.print_char('c');
     return 0;
}

But how would I get print_char to be assigned automatically, I tried this, but my compiler did not seem to like it

struct character {
     int (*print_char(int num)) = putchar;
};

Thanx in advanced.

[quzah]

You can't. You'll always have to have a "constructor". Such as:

struct character {
          int (*print_char)(int num);
};

int initcharacter( struct character *c )
{
    if( c )
    {
        c->print_char = putchar;
        return YAY;
    }
    else
        return BOO;
}

...

struct character c;
initcharacter( &c );

Quzah.

[quzah]

On second thought, you may be able to...

struct character
{
    ...
}  newcharacter = { putchar };

And from then on, do something like:

struct character instance = newcharacter;

But still, you'd have to make an assignment at creation time for it to work. Unless I'm missing something, in which case I'll blame being tired, that could do the trick. Pointers to your structure will still give you a bit of work. But no, there are no C++ style constructors in C.

And should you forget to make the assignment, and try to use the embedded function pointer, you'll have fun crashes and what not that will be a pain to track down.

Quzah.

[chrismiceli]

k, thanx.
I knew you could do this, I think I can work around the constructor though in my project.

#include <stdio.h>

int main(void) {
     struct character {
          int (*print_char)(int num);
     };
 
     struct character my_character = {
          print_char:  putchar, /* gcc extention */
     }
     my_character.print_char('c');
     return 0;
}

Or ansi way

#include <stdio.h>

int main(void) {
     struct character {
          int (*print_char)(int num);
     };
 
     struct character my_character = {
          .print_char = putchar, /* ANSI (think) */
     }
     my_character.print_char('c');
     return 0;
}