B4R Question Two Dimensional Arrays?

[daveinhull]

Hi,

Is it possible to have two dimensional arrays in B4R?
I've search the forum, but nothing comes up for B4R and the IDE/Compiler says No!

Thanks
Dave

 

[thetahsk]

...

You have to flatten the 2D matrix, create your usual 1D Array and use a mapping function to access the elements as a 2D array.

Row, Col to array index

Hello, I have 64 rows, 16 cols of 1 byte LCD, I use 1024 bytes array to store a bitmap image. in this loop I want to read array element represents col byte(convert Row, Col to array index). any Ideas? For Row = 0 To 63 For Col = 0 To 15 Index = 'row and col something...

www.b4x.com

Treating a 1D data structure as 2D grid

I am working with a native class that represents a 2D image as a 1D array. If you want to change one pixel, for example, you need to now how to derive the index from the x,y coordinates. So, let's...

softwareengineering.stackexchange.com

 

[emexes]

a mapping function

or roll your own extra dimension, eg for a 12 x 16 array:

Dim A(12 * 16)    'equivalent to Dim A(12, 16) ie both allocate 192 elements

A(5 * 16 + 8) = 42    'equivalent to A(5, 8) = 42

For I = 0 to 12 - 1
    For J = 0 to 16 - 1
        Log("A(" &  I & ", " & J & ") = " & A(I * 16 + J))    'equivalent to ... A(I, J)
    Next
Next

edit: I saw "mapping function" and thought this meant B4X Map container and massive performance hit, but in retrospect "I * 16 + J" could also be called a mapping function and perhaps my performance nerve fired unnecessarily ?

 

[thetahsk]

... my performance nerve fired unnecessarily ?

Your "friendly fire" with fluffy marshmallows has not harmed my bulletproof vest.

 

[emexes]

Your "friendly fire" with fluffy marshmallows has not harmed my bulletproof vest.

fired as in neuron activation, not as in firearm ? your reply was great except for my instinctive reflex misreaction to Map substitute for Array

 

[daveinhull]

Thanks Folk,

I ended up doing it with a mapping function into a single dimension array.
Is there any particular reason why we can't have two or multiple dimensional arrays in B4R?

Thanks
Dave