Thread: pointers to functions

Actually i am new to this pointer to functions and not able to find out what is the wrong in using the pointer to functions. The code i tried was this:

Code:

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define PI 3.1415926
double y(double);
double cos(double);
void table(double (*f)(),double,double,double);

int main()
{
     printf("TABLE OF y(x)= 2*x*x-x+1\n\n");
     table(y,0.0,2.0,0.5);
     printf("TABLE OF cos(x)\n\n");
     table(cos,0.0,PI,0.5);
     getch();
     return 0;
}
void table(double (*f)(),double min,double max,double step)
{
     double a,value;
     for(a=min;a<=max;a+=step)
        {
            value=(*f)();
            printf("%5.2f    %10.4f\n",a,value);
        }
     return;
}
double y(double x)
{
     return(2*x*x-x+1);
}

I tried in codeblocks compiler but was not able to correct although in turbo C++ it runs by some changes in the code,but not in codeblocks.Please view into it.

Originally Posted by MK27

Not quite true. That would be double (*f)(void). rakeshkool's pointer "double (f*)()" will take any number and form of argument, so it is okay. Altho "double (f*)(double)" would maybe be more optimal and at least makes the code more comprehensible, etc.

But you should call it like this:

Code:

value=f(a);

Ah, right. Yes, that's one feature of C I would *never* think of using! But yes, the real problem is the fact that the function is being invoked without arguments, as you pointed out...