* RITER, EITER: 

 The first two fields are used to implement a single iterator over the elements in the hash.
 RITER which is an integer index into the array referenced by ARRAY and EITER which is a 
 pointer to an HE. In order find the next hash element one would first look at EITER->next
 and if it turns out to be NULL, RITER is incremented until ARRAY[RITER] is non-NULL. The
 iterator starts out with RITER = -1 and EITER = NULL.