Removing blank data from an array

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300happy

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Posted: 5th Jun 2009 01:11

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Ok, I have an editor running with an array of objects. This looks somewhat like the following:

obj1,xpos,ypos,zpos,color,ect.
obj2,xpos,ypos,zpos,color,ect.

Now, when an object is deleted, I reset that array entry to "". This keeps things running in the editor, but obveously will eventually run out of IDs(I have a rather dirty system in place that will hopefully keep the ids between 1000 and 7000 for now)

Anyway, one solution I thought of was to remove the blank entries when the array is being saved. This would keep the array as a small list of what IS in the level, without saving "" lines for everything that WAS in the level but is now deleted. Basically instead of this:

obj1
obj2
BLANK SPACE WHERE obj3 WAS
obj4

I want this:

obj1
obj2
obj4

I haven't figured out how to get the length of the array for looping though. Is there a way to loop through an array, any array, without knowing the maximum limit of the array?

Basically my current problem is that the second array(the one with the deleted lines removed) becomes impossible to loop through once I remove anything from it. Since it no longer is the same length as the original, all the loops crash out with a "invalid array entry" type error because they still expect the blank rows to offset everything.

Anyone know of a solution to this, without doing something dumb like rebuilding the entire array each time I use save array?

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Vathelokai

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Posted: 5th Jun 2009 01:33 Edited at: 5th Jun 2009 01:34

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From the core commands in the help file...

+ Code Snippet

ARRAY COUNT 

This command will return the number of items in the array. This is usually the value used to create the 
array when the DIM command was used, however by modifying the dynamic array this value can change 
throughout the execution of the program. When an array is completely empty, it will return a count of -1. 
The count refers to the number of available indexes, and so will return a count of zero when the command 
DIM arr(0) is used, representing the fact a single subscript is available at index zero. 

Syntax 

Return Integer=ARRAY COUNT(Array Name(0))

+ Code Snippet

ARRAY INDEX VALID 

This command will return a value of one if the array index specified is a valid item within the array. 
Specifying a value greater or equal to the size of the array would therefore return a zero. 

Syntax 

Return Integer=ARRAY INDEX VALID(Array Name(0))

I hope this helps.

As a side note, Your camera snippet in the Code Base helped me out a lot.

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Rudolpho

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Posted: 5th Jun 2009 01:48 Edited at: 5th Jun 2009 01:49

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You could always store the array index to the saved file before each set of actual data, if that is relevant. Otherwise, just read in what you have from the file and make a new array based on that when loading.

It is always clever to save the length of an array to a file as well, if the array is supposed to be identically recreated at a later time.

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Sixty Squares

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Posted: 5th Jun 2009 03:12

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If you have a one dimensional array you could use ARRAY DELETE ELEMENT Array(0),slot to delete.

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Cagedrei

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Posted: 5th Jun 2009 07:59

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Quote: "Basically my current problem is that the second array(the one with the deleted lines removed) becomes impossible to loop through once I remove anything from it. Since it no longer is the same length as the original, all the loops crash out with a "invalid array entry" type error because they still expect the blank rows to offset everything."

Try looping backwards on the array while you remove elements. Odd things can happen when you try to iterate forwards over a shrinking array, in my experience.

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Grog Grueslayer

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Posted: 5th Jun 2009 19:31

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You can add another variable to the array that's just a 1 or a 0 to represent if the object is used 1 or is deleted 0. That way you can reuse them when you create new objects by looking for the first zero in the list of valid/deleted objects.

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bobbel

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Posted: 5th Jun 2009 20:25

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about the array index valid and array delete element commands, my experience is that they don;t work, and if they do they don;t do it good, so i suggest to just do it Grog's way cause thats easier to code i think

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Sixty Squares

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Posted: 5th Jun 2009 23:06 Edited at: 5th Jun 2009 23:06

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The array delete element command works, it just doesn't work on string or float arrays (arrays that have a $ or # sign, I just figured this out when trying to make an example). But User Defined Types can help get around that. Here's an example it uses array delete element and array count:

+ Code Snippet

Type UDT
   txt as string
endtype

DIM Array(10) as UDT


for a = 1 to Array Count(Array(0))
   Array(a).txt="obj"+str$(a)
   print "Slot ",a,": ",Array(a).txt
next a

print " "
print "Okay now time to delete slot 4."
print " "

ARRAY DELETE ELEMENT Array(0),4

for a = 1 to Array Count(Array(0))
   print "Slot ",a,": ",Array(a).txt
next a

wait key

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bobbel

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Posted: 5th Jun 2009 23:49

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oh that works, thanks Sixty Squares!

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Sixty Squares

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Posted: 6th Jun 2009 01:12

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No problem

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IanM

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Posted: 9th Jun 2009 00:38

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I'd like to see some examples of where arrays DON'T work - I'm currently not aware of any issues with arrays, and the 1D array commands.

Even the 'arrays with strings' works just fine for me:

+ Code Snippet

Type UDT
   txt as string
endtype

DIM Array(10) as string


for a = 1 to Array Count(Array(0))
   Array(a)="obj"+str$(a)
   print "Slot ",a,": ",Array(a)
next a

print " "
print "Okay now time to delete slot 4."
print " "

ARRAY DELETE ELEMENT Array(0),4

for a = 1 to Array Count(Array(0))
   print "Slot ",a,": ",Array(a)
next a

wait key

I'm pretty sure that all the next/previous/valid commands and functions work too - I use then regularly.

Utility plug-ins collection (updated 28/03/09) and
http://www.matrix1.demon.co.uk

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Sixty Squares

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Posted: 9th Jun 2009 02:48 Edited at: 9th Jun 2009 02:49

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IanM

By "Arrays with Strings" I meant this:

+ Code Snippet

DIM Array$(10)


for a = 1 to Array Count(Array$(0))
   Array$(a)="obj"+str$(a)
   print "Slot ",a,": ",Array$(a)
next a

print " "
print "Okay now time to delete slot 4."
print " "

ARRAY DELETE ELEMENT Array$(0),4

for a = 1 to Array Count(Array$(0))
   print "Slot ",a,": ",Array$(a)
next a

wait key

But I hadn't thought of doing it your way

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IanM

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Posted: 9th Jun 2009 15:23

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Just tried it - it works whether I use $ or 'as string'.

Utility plug-ins collection (updated 28/03/09) and
http://www.matrix1.demon.co.uk

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Sixty Squares

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Posted: 9th Jun 2009 22:45

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Strange, it gives me that "dbp_program.exe has encountered a problem and needs to close. We are sorry for the inconvenience." error... (DBP v7.2)

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BatVink

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Posted: 10th Jun 2009 22:59

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When deleting arrays with strings, use:

free string$()

Otherwise you will suffer from memory leakage.

Try not to keep deleting and creating array elements, as discussed here:

http://forum.thegamecreators.com/?m=forum_view&t=141494&b=1

And preferably, use a stack system as described in the editorial here...

http://www.thegamecreators.com/data/newsletter/newsletter_issue_72.html

I've been down this path, and all of the above is invaluable and worth doing before it's too late.

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Grog Grueslayer

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Posted: 11th Jun 2009 05:53

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Once I make a string it's my slave till the end of the program. They can dream about freedom all they want.

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