For information on converting to InterSystems IRIS,
see the InterSystems IRIS Adoption Guide
and the InterSystems IRIS In-Place Conversion Guide,
both available on the WRC Distributions page (login required).
Moves to the next key (atrribute name) at the location in the iteration,
and returns the associated value.
If the key is a null string (""), it starts from the beginning.
The value of key, which is passed by reference, is updated to the
key value of the returned element or null string ("") if key is at
the end of the array.