Distributed Systems Network Management (DSNM) Subsystem Interface Development Guide

Scanning a List
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109759—Distributed Systems Network Management (DSNM) Subsystem Interface
Development Guide
I Process Development Process
Scanning a List
The following examples illustrate methods of scanning lists:
•
This example scans a list forward:
@lm := _NULL;
WHILE _NOTNULL (@lm := _SUCCESSOR^LM (list,lm) DO
BEGIN
...
END;
•
In the next example, the user waits for a new last member to be added to the end of a
list by keeping a previous member pointer. After finding a _NULL, @lm is returned
to its previous setting. @lm can be used later in _SUCCESSOR^LM to retrieve a
new later member, if one has been added, or another _NULL, if one has not been
added.
@lm := @nextlm := _NULL;
WHILE _NOTNULL (@lm := _SUCCESSOR^LM (list,lm) DO
BEGIN
@nextlm := @lm;
....
END;
@lm := @nextlm;
Processing a List
Normally, you process a list either by _PUT^LM plus _GET^LM or by _PUSH^LM
plus _POP^LM, but not both. _PUT^LM is identical to _PUS^†HLM, providing
different sets of primitives for first-in, first-out (FIFO) and last-in, first-out (LIFO)
processing, respectively. Adding a list member (_PUT^LM or _PUSH^LM) allocates
new memory for the member.
Removing a member (_GET^LM or _POP^LM) does not deallocate memory
immediately: the member's memory remains allocated and its contents usable until the
next successive member is removed from the same end of the list, or a new member is
added to the same end of the list. The removed member does not participate in list scans
with _SUCCESSOR^LM or _PREDECESSOR^LM.
_UNPOP^LM and _UNGET^LM replace the last list member removed from a list with
_POP^LM or _GET^LM, respectively.