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

int hello(int n);
int goodbye(int n);

/* An fp_t is a pointer to a function that has one int argument and that
returns an int.  For example, an fp_t could hold the address of the
function hello or the function goodbye. */

typedef int (*fp_t)(int);

void f(fp_t p);

int main()
{
	f(hello);
	f(goodbye);
	return EXIT_SUCCESS;
}

void f(fp_t p)
{
	printf("%d\n", (*p)(10));
}

int hello(int n)
{
	printf("hello\n");
	return 2 * n;
}

int goodbye(int n)
{
	printf("goodbye\n");
	return 3 * n;
}