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$ZPREVIOUS (legacy function)

Returns the previous array node subscript for the specified variable.




Argument Description
variable Name of local or global array variable or the null string. It can be specified as a value, a variable, or an expression.


This page describes the legacy function $ZPREVIOUS. It is described here for compatibility with legacy applications. Use of $ZPREVIOUS is discouraged. Rather, use the form $ORDER(variable,-1).

$ZPREVIOUS returns the previous array node subscript for the specified variable. $ZPREVIOUS is similar to the $ORDER function, except that it returns the previous, rather that the next, subscript in the collation sequence.

You can use it to traverse a global in reverse subscript order. To start at the last subscript on a given level, specify the null string for the subscript reference. $ZPREVIOUS returns the null string after it returns the first subscript on the root level.

As with $ORDER, you can use $ZPREVIOUS on both local and global variables.


Given the array node definitions shown, and starting with the last subscript, $ZPREVIOUS returns the following results:

   SET ^ABC(1)=1
   SET ^ABC(2)=2
   SET ^ABC(3)=3
   SET x=$ZPREVIOUS(^ABC("")) ; 3
   WRITE !,"Third is ",x
   SET x=$ZPREVIOUS(^ABC(x))  ; 2
   WRITE !,"Second is ",x
   SET x=$ZPREVIOUS(^ABC(x))  ; 1
   WRITE !,"First is ",x
   SET x=$ZPREVIOUS(^ABC(x))  ; ""
   WRITE !,"Top is ",x

See Also

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