function_ptrs.c

// Copyright 2022 Eliot Roxbergh. Licensed under AGPLv3 as per separate LICENSE file
/*
 * Simple example of function pointers, idea from
 * http://www.simplyembedded.org/archives/battle-of-the-standards-round-2-designated-initializers/
 */

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

// I assume this is equivalent as to make these two defines separately
enum data_type { READ, WRITE };

// typedef init_t type (which is a function ptr with these characteristics)
typedef int (*init_t)(int);

// two examples of functions which falls under init_t type
int init_read(int a) { return a + 1; }
int init_write(int a) { return a - 1; }

// array of init_t, returns the approriate function pointer depending on data type (enum)
//... not to be confused, as this is just a regular array with each index specified explictly according to C99 syntax
static init_t init[] = {[READ] = init_read, [WRITE] = init_write

};

int main()
{
    int a = init[READ](5);    // call first function in array with argument 5
    int b = init[WRITE](10);  // call second function in array with argument 10
    printf("%d %d\n", a, b);
    return 0;
}