Flexible Arrays

[Mr. T]

Using a flexible array how would I eliminate an element that is NOT the last element in the array?

[[Gandalf]]

Swap it with the last element in the array, and then remove the last element.

[Mr. T]

Is this what you mean by swapping?
thing (3):= thing (upper (thing))
If not, how do you swap?

[[Gandalf]]

That's one part of swapping... But the whole process normally looks more like this:

code:

tempThing = thingB thingB = thingA thingA = tempThing

For your purposes, though, what you have is enough, since you don't really care about what the last element is when you delete it.

[Mr. T]

I did what you suggested, but I'm still getting an array subscript out of range error. I don't want to post my entire code just yet, so can I PM it to you?

[[Gandalf]]

Mr. T wrote:

I don't want to post my entire code just yet

Why not?

[Mr. T]

"theft"

[[Gandalf]]

Fine, if you really believe that is a problem...

Other people manage, even without posting their entire code. It's probably better that way too, makes it easier to help you, though occassionally it comes in handy to see the whole thing. Post only the code relevant to your problem. That way, you don't have to be worried about someone stealing your program, and we can still try and help you find the problem.

Private messages are simply not the place for help discussion, especially when you spam the same message to multiple people. That's what the help sections are for.

[Mr. T]

If I only post the relevant code, you won't be able to run the program for visual aid. Anyways, heres the section:
(the error "subscript array is out of range" occurs at this line --> item (i).check := allowableBoundries (i)

code:

type items :     record         x, y : real         size : real         vy : real %%how fast it will fall         check : boolean %%%%%oooooooooo!!!!!         %%can have more, like color, etc:     end record var item : flexible array 1 .. 15 of items var itemX, itemY : array 1 .. 15 * 30 of int var positionInItemArray : int := 1 var randomItemLocation : int := 0 proc itemInitialization     for a : 1 .. 15         for b : 1 .. 30             if grid (a, b) not= 0 then                 itemX (positionInItemArray) := a                 itemY (positionInItemArray) := b                 positionInItemArray += 1             end if         end for     end for     for i : 1 .. upper (item)         item (i).size := 2         randomItemLocation := Rand.Int (1, positionInItemArray - 1)         item (i).x := itemX (randomItemLocation)         item (i).y := itemY (randomItemLocation)         item (i).vy := -0.25     end for end itemInitialization fcn allowableBoundries (num : int) : boolean     if grid (round (item (num).x), round (item (num).y)) not= white then         result false     else         result true     end if end allowableBoundries %purpose of this array = once item starts falling, it WON't stop (even if it hits another brick) var continueMove : flexible array 1 .. upper (item) of boolean for i : 1 .. upper (item)     continueMove (i) := false end for var move : int := 0 proc moveItems     for i : 1 .. upper (item)         item (i).check := allowableBoundries (i)         if item (i).check = true then             %%not collided             continueMove (i) := true         end if         if continueMove (i) = true then             item (i).y += item (i).vy             %%move it down         end if         %item hits the paddle         if Math.DistancePointLine ((((item (i).x - 1) * 20) + 10) + item (i).size, (((item (i).y - 1) * 10) + 5) + item (i).size, (maxx div 2 - 20) + move, 8, (maxx                 div 2 + 27) + move, 8) <= item (i).size then             moneySystem             item (i).x := item (upper (item)).x             item (i).y := item (upper (item)).y             item (i).size := item (upper (item)).size             item (i).vy := item (upper (item)).vy             item (i).check := item (upper (item)).check             new item, upper (item) - 1         end if         %item reaches the bottom of the screen         if (((item (i).y - 1) * 10) + 5) + item (i).size <= 0 then             item (i).x := item (upper (item)).x             item (i).y := item (upper (item)).y             item (i).size := item (upper (item)).size             item (i).vy := item (upper (item)).vy             item (i).check := item (upper (item)).check             new item, upper (item) - 1         end if     end for end moveItems var picLargeItem : int := Pic.FileNew ("Large.GIF") var picSmallItem : int := Pic.FileNew ("Small.GIF") var randItem : flexible array 1 .. upper (item) of int for i : 1 .. upper (item)     randint (randItem (i), 1, 2) end for proc drawItems     for i : 1 .. upper (item)         if randItem (i) = 1 then             %Draw.FillOval (((round (item (i).x) - 1) * 20) + 10, (((round (item (i).y) - 1) * 10) + 5), round (item (i).size), round (item (i).size), black)             Pic.Draw (picLargeItem, ((round (item (i).x) - 1) * 20) + 6, ((round (item (i).y) - 1) * 10) + 1, picMerge)         elsif randItem (i) = 2 then             Pic.Draw (picSmallItem, ((round (item (i).x) - 1) * 20) + 6, ((round (item (i).y) - 1) * 10) + 1, picMerge)         end if     end for end drawItems

[[Gandalf]]

Mr. T wrote:

If I only post the relevant code, you won't be able to run the program for visual aid.

Yes, but it also means we won't have to sift through hundreds of lines of who knows what kind of code. If you narrow down a problem enough, it'll be a lot easier for us (or you) to find it. Though, like I said, having the complete code is also useful in some situations. You should also post what you have done to try to fix the problem, and even what you think is causing it. We shouldn't be doing all the work for you.

As for your error: In your code you are iterating through each of the items; from 1 to the amount of items at the time of the first iteration of the for loop. The problem is that you are changing the upper bound of the items inside the for loop, so the original amount of items no longer applies. Let's say you delete one item in that loop, the amount of items in now one less than it originally was, but Turing still expects the original amount of items.

Problems like this are fixed by compartmentalizing your code further, into, say checkBoundaries() and deleteItems().

[Mr. T]

I thought that maybe an exit statement right after the array update, would solve the problem. I know longer get the out of range error, but now, it seems that the entire array has shifted, and a new item is falling in the place of the item just removed from the array. Any other suggestions how can update the array?

code:

var move : int := 0 proc moveItems     for i : 1 .. upper (item)         item (i).check := allowableBoundries (i)         if item (i).check = true then             %%not collided             continueMove (i) := true         end if         if continueMove (i) = true then             item (i).y += item (i).vy             %%move it down         end if         %item hits the paddle         if Math.DistancePointLine ((((item (i).x - 1) * 20) + 10) + item (i).size, (((item (i).y - 1) * 10) + 5) + item (i).size, (maxx div 2 - 20) + move, 8, (maxx                 div 2 + 27) + move, 8) <= item (i).size then             moneySystem             item (i).x := item (upper (item)).x             item (i).y := item (upper (item)).y             item (i).size := item (upper (item)).size             item (i).vy := item (upper (item)).vy             item (i).check := item (upper (item)).check             new item, upper (item) - 1             exit         end if         %item reaches the bottom of the screen         if (((item (i).y - 1) * 10) + 5) + item (i).size <= 0 then             item (i).x := item (upper (item)).x             item (i).y := item (upper (item)).y             item (i).size := item (upper (item)).size             item (i).vy := item (upper (item)).vy             item (i).check := item (upper (item)).check             new item, upper (item) - 1             exit         end if     end for end moveItems

[Cervantes]

Read!

[Clayton]

damn Cervantes i was going to hotlink that, but apparently you get up earlier than me

now on topic:

theres one part in your code here that looks a bit weird:

Turing:

if item (i).check = true then             %%not collided     continueMove (i) := true end if if continueMove (i) = true then     item (i).y += item (i).vy             %%move it down end if

why not just move the item (i).y += item (i).vy into the first if? all your doing is making continue move true in the first one, the next thing you do is if continueMove is true is move, so you can just move that line into the first if, and be done with the second one

[Mr. T]

SuperFreak82, I know its hard to see the reason why I coded it like that. But in the game as a whole, it is neccessary. (ie. once a ball starts falling, it won't stop, even if something else is in the way)

[Mr. T]

Cervantes, I used that tutorial, and it helped eliminate the error. However, there's still a problem. It seems that another item simply takes the place of the deleted item. By this I mean that the new item falls down as if it were the original item. Can I PM someone my code so I can show what I mean.