get value of array element
tag - tag of array, specifies one of two
array types AR_...
id - array id
idx - index of an element
returns: value of the specified array element.
note that this function may return char or long
result. Unexistent array elements give zero as
a result.
string or long get_array_element(long tag, long id, long idx);
#define AR_LONG 'A' // array of longs
#define AR_STR 'S' // array of strings