Bug when redimensioning multi-dimension arrays?

[SMcNeill]

For illusttation, notice how things work out when I make both arrays lower limit 1, instead of 0:

Code: (Select All)

REDIM SHARED Grid(1 TO 5, 1 TO 5)



' LoadInitialValues

FOR y = 1 TO 5

    FOR x = 1 TO 5

        counter = counter + 1

        Grid(y, x) = counter

    NEXT

NEXT



ShowArrayValues

REDIM _PRESERVE Grid(1 TO 10, 1 TO 10)

ShowArrayValues

END







SUB ShowArrayValues

    PRINT "Array Values:": PRINT

    FOR y = 1 TO UBOUND(Grid, 1)

        PRINT USING "Row ##  "; y,

        FOR x = 1 TO UBOUND(Grid, 2)

            PRINT USING " ##"; Grid(y, x);

        NEXT

        PRINT

    NEXT

    PRINT

END SUB

REDIM PRESERVE does nothing more than preserve the memory and then move the whole block from the old array to the new array.  If you change more than the RIGHTMOST index, the structure won't read the same and your data will seem as if it's been "scrambled".  Effictively, all you can do is REDIM and PRESERVE that rightmost index -- if you need more, then you'll have to write your own routine to handle that.