B4R Question Two Dimensional Arrays?

daveinhull · Jul 6, 2020

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 · Jul 7, 2020

daveinhull said:
...

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

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Treating a 1D data structure as 2D grid

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emexes · Jul 7, 2020

thetahsk said:
a mapping function

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

B4X:

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 · Jul 7, 2020

emexes said:
... my performance nerve fired unnecessarily ?

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

emexes · Jul 7, 2020

thetahsk said:
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 · Jul 7, 2020

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

B4R Question Two Dimensional Arrays?

daveinhull

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Row, Col to array index

Treating a 1D data structure as 2D grid

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