Code: Select all
Structure player
name.s
NewList gangs.GANG() <-- This would be my second linked list
EndStructure
Yes, it helps in a way but in the example you posted in that topic (see below) if i understand it correctly, does it mean that you need to create a new streets linked list for each new element of your database ?
Code: Select all
structure StreetType
name.s
nr.w
*parent
*child
endstructure
structure DataBaseType
name.s
etc.l
*street
endstructure
newlist streets.StreetType()
newlist database.DataBaseType()
; ok now add an entry
addelement(database())
addelement(streets())
database()\name = "Vain"
database()\street = @streets()
*ptr.StreetType = @streets()
street()\name = "somewhere"
; he lives on another address too so..
addelement(street())
street()\name = "somewhere else"
*ptr\child = @street()
; now you can access this structure like this
resetlist(database())
while nextelement(database())
*ptr = database()\*street
if *ptr ; we have a street
debug *ptr\name
while *ptr\child
*ptr = *ptr\child
debug *ptr\name
wend
endif
wend
I'll have a look at it. Thanks for the tip:)Originally posted by tinman
You could use my linked list procedures whcih I posted to the resources site: http://www.reelmediaproductions.com/pb/ ... ppets.html. Linked lists inside linked lists is something I specifically wrote it for.
Code: Select all
structure GANG
Id.b
EndStructure
Structure GANGLIST
lw_Node.ListNode
*gang.GANG
EndStructure
Structure PLAYER
*mylist.ListHeader
*gangs.GANGLIST
EndStructure
Dim player.PLAYER(3)
exterminators.GANG
dll_NewList(@player(0)\mylist, SizeOf(PLAYER) - SizeOf(ListNode))
player(0)\gangs = dll_AddElement(@player(0)\mylist)
player(0)\gangs\gang = @exterminators
dll_NewList(@player(1)\mylist, SizeOf(PLAYER) - SizeOf(ListNode))
player(1)\gangs = dll_AddElement(@player(1)\mylist)
player(1)\gangs\gang = @exterminators
No. You have used pointers in some places where you should not. It's my fault, the documentation provided with the code isn't too great.Originally posted by pythagoras
Is this the good way of doing it ?
Code: Select all
xincludefile "double_linked_lists.pb"
; Simple structure for storing data about all characters
; or people (as an example)
Structure Character
c_Node.ListNode ; This must be the first item, and should be a regular variable, not a pointer
; Now you put all the data you want to store in the structure
; Only name for now since this is simple
c_Name.s ; Character name
EndStructure
; Simple structure for storing a list of gangs
Structure Gang
g_Node.ListNode ; Again, this must be first since each gang will be stored in a list
; Now your data comes here
g_Name.s ; Gang name
g_Hood.s ; Area of control
g_Members.ListHeader ; List for the members of the gang. Thie list must not be a pointer
EndStructure
DefType.ListHeader gang_list ; The main list for storing gangs
DefType.Gang *gang ; Pointer to a gang item, for working with list
DefType.Character *char ; Pointer to a character item, for working with lists
If OpenConsole()
PrintN(Str(dll_NewList(@gang_list, SizeOf(Gang) - SizeOf(ListNode))))
Repeat
Print("Enter gang name or leave blank to quit: ")
gang_name.s = Input()
PrintN("")
If gang_name""
; Gang name entered, create new item
*gang = dll_AddElement(@gang_list)
; make sure we only try to use it if successful
If *gang
*gang\g_Name = gang_name
Print("Enter area of control: ")
*gang\g_Hood = Input()
PrintN("")
; Create the list for members - you must use the full
; name to the lh_Head field due to a bug in PB you cannot
; simply use the g_Member item.
dll_NewList(@*gang\g_Members\lh_Head, SizeOf(Character) - SizeOf(ListNode))
; Now we add the gang members, in a similar way to
; when we create the gangs
Repeat
Print(" Enter member name or leave blank to stop: ")
member_name.s = Input()
PrintN("")
If member_name""
*char = dll_AddElement(@*gang\g_Members\lh_Head)
If *char
*char\c_Name = member_name
EndIf
EndIf
Until member_name=""
EndIf
EndIf
Until gang_name=""
; Now we display the contents of the lists to show you it worked
*gang = gang_list\lh_Head
While *gang
PrintN("The gang '"+*gang\g_Name+"' controls "+*gang\g_Hood+". Members are:")
*char = *gang\g_Members\lh_Head
While *char
Debug *char
PrintN("foo")
PrintN(" "+*char\c_Name)
*char = *char\c_Node\ln_Succ
Wend
PrintN("End of members")
; Move onto next item
*gang = *gang\g_Node\ln_Succ
Wend
PrintN("Freeing memory")
; Call this to free up memory in each list
; First we go to the first item in the gangs
*gang = gang_list\lh_Head
; And go round this loop until the pointer is null (end of gang list)
While *gang
; Clear the list for members of the gang
; Must use the @ symbol to get the address of the start
; of the list header inside the gang item structure
dll_DeleteList(@*gang\g_Members\lh_Head)
; Move onto next item
*gang = *gang\g_Node\ln_Succ
Wend
; Finally we must clear the main list
dll_DeleteList(@gang_list)
PrintN("Press return to exit")
Input()
CloseConsole()
EndIf
End
Your example is great and i understand my error. This is very close to what i want to achieve. I have a problem though, the example is crashing when attempting to create a second gang (ie. adding a second element to the gang_list). I'm looking into the code but can't figure the problem.No. You have used pointers in some places where you should not. It's my fault, the documentation provided with the code isn't too great.
Here is an example showing how to use linked lists inside linked lists. The main thing to get right is the way you pass a pointer to the linked lists. But generally once you have done it correctly once then it never changes. If you have more questions please ask.
I'll take a look at it and post any fixes here. It was late last night and I didn't have much chance to fully test itOriginally posted by pythagoras
to what i want to achieve. I have a problem though, the example is crashing when attempting to create a second gang (ie. adding a second element to the gang_list). I'm looking into the code but can't