Arrays

Gary Leeds

(Posted 2011) [#1]

Is it possible to define a 2 dimensional array of say 4 rows and 20 columns?

If so could someone please tell me how?

Thanks
Gary

Gary Leeds

(Posted 2011) [#2]

no worries, I found the answer


Global myarray:=[New Int[4],New Int[40]]

Function Main()

myarray[0][0]=20
myarray[0][1]=30

Print myarray[0][1]

End

muddy_shoes

(Posted 2011) [#3]

That's not doing what you think, or at least not what you said you were trying to do.

Global myarray:=[New Int[4],New Int[40]]

This doesn't declare a two dimensional 4x40 array of ints. It declares an array with two elements, one of which is a four element array of ints and one is a forty element array of ints. What you want is:

Global myarray:= [New Int[40],New Int[40],New Int[40],New Int[40]]

Midimaster

(Posted 2011) [#4]

with this code you have free choice of array size in both dimensions:

' how to call DIM a:Int[4,40] in monkey:
Global a:Int[][] =IntArray2D(4,40)


'this is only for demo purpose:
Global X%
For local i%= 0 to 3
     For local j%= 0 to 39
          X= a[i][j]
     Next
Next
end


' Function to DIM a 2-dimensional Array:
Function IntArray2D:Int[][] (X%,Y%)
	Local tmp:Int[X][]
	For Local I% = 0 Until X
		tmp[I] = New Int[Y]
	Next
	Return tmp
End Function

Loofadawg

(Posted 2011) [#5]

Global array:Int[64]

'array[x+(8*y)]  for an 8x8 array
'array[x+(16*y)] for a 4x16 array
'array[x+(32*y)] for a 2*32 array

For y = 1 to 6
   For x = 1 to 6
      array[x+(8*y)] = 1
   Next 
Next

..
..
..

For y = 0 to 7
   For x = 0 to 7
      If array[x+(8*y)]
         SetColor 255,255,255
      Else
         SetColor 127,127,127
      End If
      DrawRect x*32,y*32,30,30
   Next
Next

You can create a function to make sure everything stays within the confines of the dimensions. Not sure how efficient this is, but it works.

Gary Leeds

(Posted 2011) [#6]

cheers for the tips, as I mentioned in the IOS forum its strange how HTML5 never picked up on the error but IOS does.

Least I know how to do it properly now

Thanks

muddy_shoes

(Posted 2011) [#7]

its strange how HTML5 never picked up on the error but IOS does.

Javascript arrays automatically resize as you add elements so it's not an error in that language.

Samah

(Posted 2011) [#8]

Also, the deeper you go, the more objects are created. This is bad if you're working with Android, or any heap-based language. [4][40] will create 5 objects, but [40][4] will create 41 objects. That's a lot. Don't even think of storing large levels for a tile-based engine like that!

If you're going for performance, I'd suggest just sticking with a 1D array and indexing it arithmetically.

muddy_shoes

(Posted 2011) [#9]

Samah, have you tested the performance issues on the various platforms? I've done some testing on HTML5 (FF&Chrome), Flash and GLFW and I'm not seeing a major performance win to be had by doing your own index arithmetic.

Even where there is a performance gain it doesn't seem worth the overhead of tracking the intended row sizes manually. The only places I can see some value are edge-cases, such as completely resetting the values in an Array, or perhaps if you were doing nothing but iterate over a large array, such as in a cellular automata.

Gary Leeds

(Posted 2011) [#10]

Am I right in thinking that 3 dimensional arrays are not possible with Monkey and I would have to use a 1D and index it?

muddy_shoes

(Posted 2011) [#11]

It's just an extension of the 2D case. Here's a helper function.

Function AllocateArray:Int[][][]( i:Int, j:Int, k:Int, initial:Int)
    Local arr:Int[][][] = New Int[i][][]
    For Local ind = 0 Until i
        arr[ind] = New Int[j][]
        For Local ind2 = 0 Until j
	    arr[ind][ind2] = New Int[k]
	    For Local ind3 = 0 Until k
	        arr[ind][ind2][ind3] = initial
	    Next
        Next
    Next
    Return arr		
End

Gary Leeds

(Posted 2011) [#12]

Cheers Muddy