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

int main (int argc, char **argv) {
	char *name[7] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
	char **string_ptr;
	int i;
	int arr[10][12];
	int *whatever;
	
	whatever = arr[6]; /* legal */
	/* arr[6] = whatever;  illegal */
	arr[6][5] = 47; /* legal */
	arr[2][27] = 5; /* legal; equivalent to arr[4][3] = 5; */
	printf ("arr[4][3] = %d\n", arr[4][3]);
		
	string_ptr = "hello"; /* legal but a bad idea! Does an implicit cast from char * to char **    */
	/* printf ("string_ptr = %x; *string_ptr = %s\n", string_ptr, *string_ptr);    crashes because *string_ptr is an invalid pointer */
	string_ptr = (char **)calloc(10, sizeof(char *));
	printf ("string_ptr = %x; *string_ptr = %s\n", string_ptr, *string_ptr);
	string_ptr = &name[0]; /* or equivalently string_ptr = name; */
	printf ("string_ptr = %x; *string_ptr = %s\n", string_ptr, *string_ptr);
	name[0] = malloc(7);
	printf ("string_ptr = %x; *string_ptr = %s\n", string_ptr, *string_ptr);
	strcpy (name[0], "Sunday");
	printf ("string_ptr = %x; *string_ptr = %s\n", string_ptr, *string_ptr);
	name[0] = name[1] = "Snarkday";
	printf ("string_ptr = %x; *string_ptr = %s; string_ptr[0] = %s; string_ptr[1] = %s\n", string_ptr, *string_ptr, string_ptr[0], string_ptr[1]);
	name[1] = "Greenday";
	printf ("string_ptr = %x; *string_ptr = %s; string_ptr[0] = %s; string_ptr[1] = %s\n", string_ptr, *string_ptr, string_ptr[0], string_ptr[1]);
	name[2] = "Blueday";
	name[3] = "Yellowday";
	/* etc. */
	
	/* other_name[0] = "hello"; */
	/* name[1][0] = 'M';      crashes because name[1] points to the literal string "Greenday" which lives in a read-only region of memory */
	name[1] = strdup(name[1]);    /* strdup is basically a malloc followed by a strcpy */
	name[1][0] = 'M';	/* now this works */
	name[1][1] = 'o';
	printf ("string_ptr = %x; *string_ptr = %s; string_ptr[0] = %s; string_ptr[1] = %s\n", string_ptr, *string_ptr, string_ptr[0], string_ptr[1]);
	
	for (i = 0; i<7; ++i)
		printf ("name[%d] = %s\n", i, string_ptr[i]);

	printf ("Another day is %s\n", name[4]);
	/* printf ("other_name is %s\n", other_name); */

	for (i=0; i<argc; ++i)
		printf ("argv[%d] = %s\n", i, argv[i]);
	return 0;
	}