Question

If I allocate a C array like this:

int array[ 5 ];

Then, set only one object:

array[ 0 ] = 7;

How can I check whether all the other keys ( array[1], array[2], …) are storing a value? (In this case, of course, they aren’t.)

Is there a function like PHP’s isset()?

if ( isset(array[ 1 ]) ) ...

Answer 1

There isn’t things like this in C. A static array’s content is always “set”. You could, however, fill in some special value to pretend it is uninitialized, e.g.

// make sure this value isn't really used.
#define UNINITIALIZED 0xcdcdcdcd

int array[5] = {UNINITIALIZED, UNINITIALIZED, UNINITIALIZED, UNINITIALIZED, UNINITIALIZED};

array[0] = 7;

if (array[1] != UNINITIALIZED) {
   ...