Link list
BlitzPlus Forums/BlitzPlus Programming/Link list
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| Can any body help me? can Somebody provide me with a sample of a link-list if possible? I knew how to use them in c but I have not used them in B+. so I don't know it this is possible. |
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| I thought there was an example in the blitz docs or the samples folder, but I'm at work right now nd can't check. Or it might have been on Blitz Coder. Also check the code archives on this this. |
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Apparently, lists are handled a bit differently now. They use Types. Here's an example from the manual:; Define a crafts Type Type crafts Field x Field y Field dead Field graphic End Type ; Create 100 crafts, with the unique name of alien For t = 1 To 100 alien.crafts = New crafts alien\x = Rnd(0,640) alien\y = Rnd(0,480) alien\dead = 0 alien\graphic = 1 Next ; Move to the first object alien.crafts = First crafts Print alien\x Print alien\y Print alien\dead Print alien\graphic ; move to the next alien object alien = After alien Print alien\x Print alien\y Print alien\dead Print alien\graphic ; move to the last alien object alien.crafts = Last crafts Print alien\x Print alien\y Print alien\dead Print alien\graphic ; move to the second to the last alien object alien = Before alien Print alien\x Print alien\y Print alien\dead Print alien\graphic There doesn't seem to be a NewList command et al like before... Just the syntax has changed I guess. All the same functionality is there, though. Russell |
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| You can still make a linked list where one object points to the next in the list and if you delete one you must alter the previous one in the list etc. I don't have a use for them in my game at the moment, but for windows apps. they are pretty useful, things like StringLists for example. |
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| Thanks a lot guys. That was helpfull. I am creating a game in which unlimited parts and weapons of differnt sort are aded to vehircles. a child pointer for weapons and a child pointer for parts. of course all inclusive for the same parent. ... I created the program below in c and was able to convert it to B+. by looking at some samples. It is not thouroughly documented but it is fairly easy to understand. AppTitle "Test Engine" ; menu constants for event processing Const FILELOAD=1 Const DISPLAYFILE=2 Const FILESAVE=3 Const FILEQUIT=4 Const HELPABOUT=5 Const REMOVEFILE=6 Const BACKGROUND= 1 Global box,test,testactive,decoding Global filename$ testactive = False decoding = False Type file Field strng$ End Type Type option Field included$ End Type Type element Field Question$ Field firstchoice.option Field lastchoice.option Field firstanswer.option Field lastanswer.option Field selected Field correct End Type ; open a window so we can show off our menu window=CreateWindow("A+ test review",40,40,600,600) ; create the menu menu=WindowMenu(window) file=CreateMenu("File",0,menu) CreateMenu "Load",FILELOAD,file CreateMenu "&Display",FILENEW,file CreateMenu "Save",FILESAVE,file CreateMenu "Close",REMOVEFILE,file CreateMenu "Quit",FILEQUIT,file help=CreateMenu("Help",0,menu) CreateMenu("About",HELPABOUT,help) UpdateWindowMenu window box=CreateTextArea (0,0,GadgetWidth(window)-20,GadgetHeight(window)-70,window) SetTextAreaColor(box,0,0,0,BACKGROUND) ; background SetTextAreaColor(box,255,255,0) Repeat Select WaitEvent() Case $1001 ;menu event Select EventData() Case FILELOAD: If testactive Then filename$=RequestFile("Load Practice test","txt") If Len(filename$) Then Deleteoldtest loadtest EndIf Else filename$=RequestFile("Load Practice test","txt") If Len(filename$) Then loadtest EndIf EndIf Case DISPLAY: showfile Case REMOVEFILE: If testactive Then Deleteoldtest Else Notify "No file to delete" EndIf Case FILESAVE: filename$=RequestFile("Save File",filename$,True) Case FILEQUIT: End Case HELPABOUT Notify "selecting About = user interest" End Select Case $803: ;close window event deleteoldtest End End Select Forever Function loadtest() test = ReadFile(filename$) If test Then While Not Eof(test) raw$ = ReadLine(test) Trim$(raw$) If Len(raw$) Then If Left$(raw$,1)= "~" Then current.element = New element current\firstchoice.option = Null current\lastchoice.option = Null current\firstanswer.option = Null current\lastanswer.option = Null current\question$ = Replace$(raw$,"~","") testactive = True Else If Left$(raw$,1) >= "A" And Left$(raw$,1)<="Z" Then temp.option = New option If current\firstchoice = Null Then current\firstchoice.option = temp.option current\lastchoice.option = temp.option EndIf temp\included$ = raw$ Insert temp.option After current\lastchoice.option current\lastchoice.option = temp.option EndIf If Left$(raw$,1) = "@" Then temp.option = New option If Current\firstanswer.option = Null Then current\firstanswer.option = temp.option current\lastanswer.option = temp.option EndIf temp\included$ = Replace$(raw$,"@","") Insert temp.option After current\Lastanswer.option current\lastanswer.option = temp.option EndIf EndIf EndIf Wend CloseFile(test) Else Notify"Error: file not found" EndIf End Function Function showfile() SetTextAreaText(box,"",0,TextAreaLen(box),2) If testactive Then For current.element = Each element AddTextAreaText(box, Chr$(13)+current\question$+Chr$(13)) temp.option = current\firstchoice.option While temp.option <> Null AddTextAreaText(box, temp\Included$+Chr(13)) If temp.option= current\lastchoice.option Then Exit temp.option = After temp.option Wend temp.option = current\firstanswer.option While temp.option<>Null AddTextAreaText(box,temp\included$+Chr$(13)) If temp.option= current\lastanswer.option Then Exit temp.option = After temp.option Wend Next Else Notify("Load a file first",1) EndIf End Function Function deleteoldtest() If testactive Then SetTextAreaText(box,"",0,TextAreaLen(box),2) For current.element = Each element temp.option = current\firstchoice.option For temp.option = Each option Delete temp Next temp.option = current\firstanswer.option For temp.option = Each option Delete temp Next Delete current Next testactive =0 EndIf |
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| The conventional way to build a linked list is to put all your values in an array then create a seperate array full of pointers. Take the List n... 4 7 2 5 1 Now look at the pointers... initial vector is 5 N > P ----- 4 > 4 7 2 > 1 5 > 2 1 > 3 The initial vector points to 5th in the list because 1 is the lowest. 1 Points to 3rd in list because 2 is the next highest.2 points to 1 because 4 is the next highest etc... The advantages of doing it this way is that you just sort the pointers, not the actual list. |
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| Yes, I understand that well. I knew about that, but my lazy vocabulary failed to properly express my intention... I finally learned how to do both in B+. Thanks all of you who showed interest in my request. |
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