emulating partial function application in c

Question

I\'m writing a C program that would, if had been a part of the language, benefit from, partial function application. I need to supply a function pointer with a fixed signatu

Answer 1

I don't know of any straight foward way do do what you want, since C doesn't support closures or any other way to pass "hidden parameters" to your functions (without using globals or static variables, strtok style)

You seem to come from a FP background. In C everything has to be done by hand and I'd risk saying that in this case it might be better to try to model things in OO style instead: turn your functions into "methods" by making them receive an extra argument, a pointer to a struct of "inner attributes", the this or self. (If you happen to know Python this should be very clear :) )

In this case, for example, func1 might turn into something like this:

typedef struct {
     int code;
     char * name;
} Joystick;

Joystick* makeJoystick(int code, char* name){
    //The constructor
    Joystick* j = malloc(sizeof Joystick);
    j->code = code;
    j->name = name;
    return j;
}

void freeJoystick(Joystick* self){
    //Ever noticed how most languages with closures/objects
    // have garbage collection? :)
}

void func1(Joystick* self){
    func2(self->code, self->name);
}

int main(){
     Joystick* joyleft  = make_Joystick(10, "a string");
     Joystick* joyright = make_Joystick(17, "b string");

     func1(joyleft);
     func1(joyright);

     freeJoystick(joyleft);
     freeJoystick(joyright);

     return 0;
}