// The main function that will be run when the file is run from bash
int main(int argc, char *argv[])
{
// make two Person structures and then create pointers to them
struct Person *joe = person_create(
"Joe Alex", 32, 64, 140);
struct Person *frank = person_create(
"Frank Black", 20, 72, 180);
// Print out where each is in memory (possible because they are lvalues)
printf("Joe is at memory location %p:\n", joe);
person_print(joe);
printf("Frank is at memory location %p:\n", frank);
person_print(frank);
// We can do assignment to the variables we assigned for our Person struct
joe->age += 20;
joe->height -= 2;
joe->weight += 40;
person_print(joe);
frank->age += 20;
frank->weight += 20;
person_print(frank);
// Clean the structs out of memory before the program ends
person_destroy(joe); // valgrind shows leaked bytes if not called
person_destroy(frank);
// person_destroy(NULL); // passing NULL causes SIGABRT error
return 0;
}
/*
this program illustrates how to use void* as a generic pointer, how
to use pointer casts to get the generic pointer interpreted
according to what type of value it points to, and the danger of
making an incorrect cast
*/
int main (int argc, char ** argv)
{
struct tm now; /* standard struct for storing a time value */
double lightspeed;
Person * albert; /* pointer to our custom struct person */
void * generic_pointer;
/*
let's read the clock, it gets stored in a standard struct tm (from
the time.h header)
*/
if (0 != clock_read (&now)) {
printf ("failed to read the clock\n");
return 1;
}
/*
the speed of light as a double-precision floating point number
*/
lightspeed = 299792458.0;
/*
Albert Einstein was born on March 14, 1879. His age depends on
today's date...
*/
albert = person_create ("Albert Einstein",
(now.tm_mon >= 3 && now.tm_mday >= 14) ?
now.tm_year + 1901 - 1879 :
now.tm_year + 1900 - 1879);
/* **************************************************
* NOW FOR THE FUN PART *****************************
* **************************************************/
/*
the generic pointer can store the address of any of our variables
*/
generic_pointer = &now;
printf ("the date and time is\n");
clock_print (&now);
generic_pointer = &lightspeed;
printf ("the speed of light is\n %g m/s\n", *(double*)generic_pointer);
generic_pointer = albert;
printf ("the person is\n");
person_print (generic_pointer);
return 0;
}
