$List_Global and $List_Session

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$List_Global and $List_Session: Access/create global/session $list

Note: Many $functions have been deprecated in favor of Object Oriented methods. There is no OO equivalent for the $List_Global and $List_Session functions because of the OO ability to declare any object Global or Session (that is, this function is part of Stringlist declaration).

$List_Global and $List_Session return a $list identifier by which one may refer to a global or session $list in a request. The global or session $list may be one that already exists because of a previous $List_Global, $List_Session, or $ListSave function, or it may be created by the $List_Global or $List_Session function.

Syntax

%result = $List_Global(name, [type])

%result = $List_Session(name, [type])

%resultA numeric variable set to the identifier of the global or session $list, or set to a negative error code if an error occurred. Possible error codes are:
-3No room in CCATEMP to add global name
(not possible with OLD)
-14No global list for name (for type OLD)
Already a global list for name (for type NOTOLD)
-15Invalid type value
nameThe name of the global or session $list. This is a required argument.
typeThe type of processing $List_Global or $List_Session is to perform. Valid values are the following:
ANY If the global or session $list already exists, it is referenced with its current contents. If it does not exist, a new empty global or session $list is created.
OLD The global or session $list must already exist, that is, it must have been created with a previous $List_Global or $List_Session or saved with a $ListSave.
NEW The global or session $list must not already exist. If it does, it will be recreated.
PREP Same as ANY but empties $list if it has data.
PREPANY Same as ANY but empties $list if it has data.
PREPOLD Same as OLD but empties $list if it has data.
PREPNEW Same as NEW.
ANYPREP Same as ANY but empties $list if it has data.
OLDPREP Same as OLD but empties $list if it has data.
NEWPREP Same as NEW.

This is an optional argument that defaults to ANY.

Usage notes

  • A particular instance of $List_Global or $List_Session always returns the same $list identifier so it cannot be called multiple times for different global or session $list names to allow simultaneous reference to these $lists.
  • The scope of a $List_Global or $List_Session identifier is the evaluation of the SOUL request in which it was contained. When evaluation is over, global $list data appears exactly like a $ListSave'd (or $ListSav'ed) $list and, in fact, can be $ListRst'ed. For a different request to access that same global $list, it must issue a $List_Global or $ListRst with the same name. A $List_Global can also be issued against a $list that was $ListSave'd, even in the same procedure, as in the following example:

    %rc = $ListSave(%list, 'NEW.NAME') %glist = $List_Global('NEW.NAME')

  • A $List_Session cannot access a $ListSave'd $list, and $ListRst cannot access a session $list.
  • Separate $List_Global or $List_Session statements can be issued against the same name. If this is done, each instance of $List_Global or $List_Session will return a separate $list identifier, but they will actually refer to the same underlying $list. For example, the result of the following $List_Global statements is a single global $list with name WHATEVER that contains two items: WASTE NOT is the first, and WANT NOT is the second:

    %list1 = $List_Global('WHATEVER', 'NEW') %list2 = $List_Global('WHATEVER') %rc = $ListAdd(%list1, 'WASTE NOT') %rc = $ListAdd(%list2, 'WANT NOT')

  • A $ListImg on a global $list identifier is associated with the $list identifier, not the underlying data, so in the case of multiple $List_Globals or $List_Sessions for the same name, the $ListImg only applies to the $list identifier for which it was issued. For example, the first $ListAddI below adds data to the global $list from image MYIMAGE, while the second $ListAddI adds data from image YOURIMAGE:

    %list1 = $List_Global('WHATEVER', 'NEW') %list2 = $List_Global('WHATEVER') %rc = $ListImg(%list1, %MYIMAGE:COUNT) %rc = $ListImg(%list2, %YOURIMAGE:COUNT) %rc = $ListAddI(%list1) %rc = $ListAddI(%list2)

  • Global and session $list names are kept in CCATEMP. For every $List_Global or $List_Session call, logical I/O (and possibly physical I/O) must be performed to look up the name. As such, it is a good practice to avoid $List_Globals or $List_Sessions for constant names inside a loop, and to make global and session $list identifier variables COMMON rather than letting each subroutine issue a $List_Global or $List_Session function.
  • If it is uncertain whether the global or session list has been already declared inside a subroutine (or anywhere for that matter), code like the following can be used to ensure that the $List_Global or $List_Session statement is only issued once:

    IF NOT %MY.LIST THEN %MY.LIST = $List_Global('MY.LIST', 'ANY') END IF

  • The PREP prefix or suffix for all the types indicates that the returned $list should be cleared of its contents. For example, after

    %LIST1 = $List_Global('WHATEVER', 'NEW') %RC = $ListAdd(%LIST1, 'WASTE NOT') %LIST2 = $List_Global('WHATEVER', 'PREPOLD') %RC = $ListAdd(%LIST2, 'WANT NOT')

    the global $list identified by WHATEVER would have a single item with content WANT NOT. Just as type ANY is the default for $List_Global, PREP is the same as PREPANY.
  • Global $lists can only be restored with a $ListRst if they have not been accessed as $List_Global in the procedure that issues the $ListRst. You can clean up any global $lists with $List_Global_Del, which can be issued whether or not a name was referenced in the current procedure with a $List_Global. You can clean up any session $lists with $List_Session_Del, which can be issued whether or not a name was referenced in the current procedure with a $List_Global.
  • $List_Global and $List_Session have independent namespaces. That is, the same name used for $List_Global and $List_Session reference different $lists.
  • A $List_Session call when there is no session open causes a request cancellation.

Products authorizing $List_Global and $List_Session

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