Array 1D - 2D, i'm confused

[MyEarth]

#include <Array.au3>

Local $aArray1D[3] = [1, 2, 3]
Local $aArray2D[3][3] = [[1, 2, 3],[2, 3, 4],[3, 4, 5]]

ReDim $aArray2D[3][1]
_ArrayDisplay($aArray1D)
_ArrayDisplay($aArray2D)

ReDim $aArray2D[3]
_ArrayDisplay($aArray2D)

The first ReDim, from what i see $aArray1D and $aArray2D are equal. So why if i'll try to ReDim the 2D in 1D i lost the data? There is a way to convert a 2D array to 1D without loop and having only the value like the 1D one?

[Melba23]

MyEarth,

Although the 2 arrays look identical, they are in fact very different. A 1D array is perhaps best thought of as a simple list, whereas a 2D array can be thought of as a grid with a variable number of columns. If you look at the bottom left of each _ArrayDisplay dialog you will see that the arrays are different ([3] for the 1D and [3][1] for the 2D).

As you have discovered, you cannot change the number of dimensions with ReDim and retain the existing data - mainly because of the way AutoIt stores the data for the 2 types of array - although you can change the number of rows/columns within each dimension.

However, there is a way to get a 2D array into a 1D array - just use _ArrayColDelete to delete the unwanted columns and set the $bConvert parameter to True:

#include <Array.au3>

Local $aArray2D[3][3] = [[1, 2, 3],[4, 5, 6],[7, 8, 9]]

_ArrayColDelete($aArray2D, 1, True)
_ArrayColDelete($aArray2D, 1, True)
_ArrayDisplay($aArray2D)

How does that work for you?

M23

[MyEarth]

Hi,

_ArrayColDelete work but will loop everything. I know the array are different [3] and [3][1] but they not both store the information in the same index? So in theory ReDim, since the index is the same, need to store the information not delete them...i think 

[BrewManNH]

You think incorrectly. If using ReDim to convert a 2D to a 1D array, you WILL lose the information in the array. The help file explains this. Whether you'd like it to work that way or not isn't a valid point, because it doesn't work that way.

[Melba23]

MyEarth,

As I explained above, you cannot change the number of dimensions with ReDim and also retain the existing data. Once again: 1D and 2D arrays are not the same and $aArray1D[1] is not the same as $aArray2D[1][0] as (to the best of my knowledge) AutoIt stores the data internally in a completely different manner.

M23