The GetListPrevious() function retrieves the Previous position index (from the current index) from the queried linked list. If the current index is the first in the list, then GetListPrevious will return a -1. Since there's no item before the first item.
FACTS:
* Don't know what a linked list is ?, make sure you read the LinkedLists tutorial then.
Mini Tutorial:
This example creates a list of three people, then runs through the list manually and displays each persons names and their list position.
; Declare the "Person" user defined type.
Type Person
; These Fields will hold this persons name
FirstName$
SurName$
EndType
; Dimension the Friends variable of type Person,
; with linked list support
Dim Friends As Person List
; Add a person (Billy) to Friends list
Friends= New Person
Friends.FirstName$ ="Billy"
Friends.Surname$ ="Citizen"
; Add another person (Sally) to Friends list
Friends= New Person
Friends.FirstName$ ="Sally"
Friends.Surname$ ="Stevens"
; Add another person (Sally) to Friends list
Friends= New Person
Friends.FirstName$ ="Olivia"
Friends.Surname$ ="Dude"
; Aak the list what cell is at the front/start of the list
ThisLInk=GetListFirst(Friends())
;Enter a while loop providing the link is above 0
While ThisLink>0
; Manually Set our Current position in the list
SetListPos Friends(),ThisLInk
; Display this persons name
Print Friends.FirstName$+" "+Friends.Surname$
; Display this index of back of the previous list item
Print "Prev Position="+Str$(GetListPrevious(Friends()))
; Display this index of our current position within the list
Print "List Position="+Str$(GetListPos(Friends()))
; Display this index of the next item in the list
Print "Next Position="+Str$(GetListNext(Friends()))
Print ""
; Ask the list for the Next LINK to move forward through
; the list.
ThisLink=GetListNext(Friends())
EndWhile
; display the screen and wait for a key press
Sync
WaitKey
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This example would output.
Olivia Dude
Prev Position=-1
List Position=3
Next Position=2
Sally Stevens
Prev Position=3
List Position=2
Next Position=1
Billy Citizen
Prev Position=2
List Position=1
Next Position=-1
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