multidimensional array questions

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Turoid

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Posted: 29th Apr 2011 21:25

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Hello

Just picked up dbpro again in my spare time, have some questions about array's.

For example, I want to add an element at the second index of this array:

NOTE: psuedo code kind of

+ Code Snippet

dim MyArray(1,0) as string

Element as string
Element = "Just another element"

// I want something like this:
MyArray(1).add(Element)

// So it becomes:
MyArray(1,1) = Element

Another question. How can I get the seperate array count values of this array. I want to know the count of index 1 itself, but also per index the count of the second index. Like so:

+ Code Snippet

dim MyArray(3,0) as string

// Add some elements here
... see question above

// something like
FirstIndexCount = MyArray().count 
//represents the count of MyArray(THIS COUNT,0) 

SecondIndexCount = MyArray(1).count
//represents the count of MyArray(1,THIS COUNT)

I can imagine it could be quite difficult for you guys to understand what I'm asking. But the array commands for adding, removing and counting array elements just don't work that well for me. Unless I'm using them wrong, which I think is the case.

Also I couln't find any clear examples which showed me a solution. I know about redimming, but then I still have the issue of 'counting' the amount of elements from a second or third element in an array.

Thanks in advance

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tiresius

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Posted: 29th Apr 2011 21:29

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You cannot have dynamically sized multi-dimension arrays. Meaning, they can't grow through use (adding an element) without the redim command first. You might want to look into DarkData if you're trying to use a fancy table type data structure.

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KISTech

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Posted: 29th Apr 2011 21:32

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You're referring to treating the array as an object, and it doesn't work that way in DBP.

dim MyArray(10) as string
MyArray(1) = "one"
MyArray(2) = "two"
...

Simple no frills BASIC.

The count of the first index is the important one. You have to set the second one when you create the array, and that's what it stays at. You can't add or subtract from the second index at runtime.

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IanM

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Posted: 30th Apr 2011 02:09 Edited at: 30th Apr 2011 02:14

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You can resize and existing multi-dimensional array - you simply use the DIM command on it again:

+ Code Snippet

' Dimension the array
dim MyArray(1,0) as string

` do some stuff

` Now enlarge the 2nd dimension of the array
dim MyArray(1,1) as string

[edit]Just read the last bit of the original question.

Quote: "but then I still have the issue of 'counting' the amount of elements from a second or third element in an array."

There is no such thing. DBPro arrays are rectangular.

DIM a(10,10) will define an array of 11 by 11 cells (numbered from 0 to 10). DIM a(1, 2, 3) will define an array of 2 by 3 by 4 cells. You can't have line 0 of the array a different size from line 1 etc.

[one more edit]Rather than ask us how to implement your solution, why not tell us what the problem you're trying to solve is.

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Turoid

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Posted: 30th Apr 2011 15:06 Edited at: 30th Apr 2011 15:08

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Thanks all for the replies

I now better understand how arrays work within DBPro.

I currently use DBPro to do some prototyping of algorithms I find interesting. Much faster to do these kind of things with DBPro rather than setting up a complete project using SDL for example.

I found this work around:

+ Code Snippet

// My array as follows:
Dim NodeConnectionList(1,1)

// NodeConnectionList( NodeID, List which contains the linked nodes of this node)
// The first etry of the second index always contains the count of linked nodes, which in fact is the count of the elements of the second index .. Hope I make myself clear, hard to explain :)


// Now When I add another 'connection' to a node, I do this:

// get the current size of the 'connectionlist' from node '1'
tNodeConnections = NodeConnectionList(1,1)
// Increase the list by 1 element
Dim NodeConnectionList(1,tNodeConnections+1)
// Fill it
NodeConnectionList(1,tNodeConnections+1) = "SomeAnotherNodeToBeConnectedTo"

You might wonder where this all is for. Some time ago I did an attempt on a* pathfinding, which used a 'grid' to calculate everything. I found that this grid was quite limited, also not as optimized as a custom 'navigation mesh' for example could be. Therefor I wanted to try something with nodes linked together to let my a* search on.

Got it working, you can view it here

http://www.youtube.com/watch?v=98RNGFv9h9Q

Thanks again, DBPro is really nice for quick prototying of ideas for this kind of little systems. Though I would like to have a feature which lets us use arrays within types, solves a lot of issues

!

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KISTech

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Posted: 30th Apr 2011 17:18

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That's pretty cool. Nicely done.

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Diggsey

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Posted: 30th Apr 2011 21:54

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@Turoid
I made a DBPro plugin for node based A* pathfinding

[b]

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KISTech

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Posted: 1st May 2011 04:41

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Also nicely done.

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IanM

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Posted: 1st May 2011 13:33

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@Turoid,
Call me a naysayer, but I'm not sure that I see anything great about your solution, or why it even works

1. If the first dimension can change, then if the second row of the 2-D array has less items in it that the first row, you'll lose most data in the first row if not careful. (I suspect he has NOT used this method).

+ Code Snippet

dim MyData(3, 0)

AddToRow(1, 9)
AddToRow(1, 99)
AddToRow(1, 999)

AddToRow(2, 8)
AddToRow(2, 88)

for i = 1 to MyData(1, 0)
    print MyData(1, i)
next

wait key
end

function AddToRow(Row as integer, Value as integer)
    inc MyData(Row, 0)
    Dim MyData(Row, MyData(Row, 0) )
    MyData(Row, MyData(Row, 0)) = Value
endfunction

2. If you're simply using it as a 1-D array (ie, the first dimension never changes size), then you may as well use a 1-D array rather than have the extra dimension and double the memory usage. (It doesn't sound like he's done that either).

Either you've not explained the whole solution, or your code is working by coincidence (at least as far as I can see).

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DLS

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Posted: 2nd May 2011 01:37

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i remember back when i was in college playing with VB they had a redim command that allowed you to grow an array iirc

but that was a long long time ago and i may now be barking up the wrong tree. still would be a handy feature to have i guess

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IanM

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Posted: 2nd May 2011 15:26

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DIM does the same job for DBPro. To lose the data in an array, you need to actually UNDIM it before re-DIM-ing it to its new size.

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DVader

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Posted: 2nd May 2011 16:55 Edited at: 2nd May 2011 16:57

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Well, as DB had problems when first released with resizing arrays, I have always gone down the route of simply making them larger than needed. Not super efficient, but it generally works ok. Still it could cause issues if you need to check through lots of data I suppose. Does anyone know if the array commands actually work ok now?

+ Code Snippet

EMPTY ARRAY : EMPTY ARRAY Array Name(0)
ARRAY INSERT AT TOP : ARRAY INSERT AT TOP Array Name(0)
ARRAY INSERT AT BOTTOM : ARRAY INSERT AT BOTTOM Array Name(0)
ARRAY INSERT AT ELEMENT : ARRAY INSERT AT ELEMENT Array Name(0), Index
ARRAY DELETE ELEMENT : ARRAY DELETE ELEMENT Array Name(0)
NEXT ARRAY INDEX : NEXT ARRAY INDEX Array Name(0)
PREVIOUS ARRAY INDEX : PREVIOUS ARRAY INDEX Array Name(0)
ARRAY INDEX TO TOP : ARRAY INDEX TO TOP Array Name(0)
ARRAY INDEX TO BOTTOM : ARRAY INDEX TO BOTTOM Array Name(0)
ARRAY INDEX TO QUEUE : ARRAY INDEX TO QUEUE Array Name(0)
ADD TO QUEUE : ADD TO QUEUE Array Name(0)
REMOVE FROM QUEUE : REMOVE FROM QUEUE Array Name(0)
ARRAY INDEX TO STACK : ARRAY INDEX TO STACK Array Name(0)
ADD TO STACK : ADD TO STACK Array Name(0)
REMOVE FROM STACK : REMOVE FROM STACK Array Name(0)

I never had any luck using these commands in the past and so have ignored them for years. I tend to use old school methods with arrays rather than these commands, which so far has been fine. As IamM mentioned, undim and then diming an array again should work, you just have to put the data back into it afterwards.

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Grog Grueslayer

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Posted: 2nd May 2011 18:18

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Those commands unfortunately only work for 1D arrays but they do work well. What I do on my current project (a huge database) when I need one more record beyond the array size I redim it for 100 more elements.

+ Code Snippet

    ` Check if the next record will go beyond the array size
    if Record>MaxRecord
     ` Increase MaxRecord by 100
     inc MaxRecord,100
     ` Redim all the arrays needed
     dim Card(MaxRecord) as CardInfo          ` Card Data
     dim People(MaxRecord,17) as AllPeople    ` 0=Husband 1=Wife  2-17 = Everybody else
     dim Calendar(MaxRecord,365) as Year      ` 366 days (1 for leap year)
     dim List(9,MaxRecord) as CardList        ` List of Cards for main menu
    endif

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Agent

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Posted: 3rd May 2011 08:00

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I can confirm that these array commands do work, but I'm not a fan of automatic processing like this. I think it's a better idea to resize the array manually, and deploy your data to the newly defined element.

Can't rightly say why I don't like the array commands. It just feels like an automated process, and I hate anything automated. I like to work at the lowest possible level when coding (I don't like using plugins unless they are truly excellent, for example).

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DVader

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Posted: 7th May 2011 17:46

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Agent, I tend to feel the same way. Although after playing about trying to get DB to have a decent text input, I sometimes think a nice VB text box would be very useful. I mainly only have a problem with automation if it slows things down too much though. If it ran as fast and introduced no bugs I would probably be happy enough.

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