array assigned in SUBs

[TerryRitchie]

Thanks Terry ! didnt know ReDim x(0) as Integer is ok ?

You're welcome. Glad I could help.

DIM and REDIM will accept any index value(s) for an array. All legal:

DIM x(-1 TO 10) AS <your_type_here>
DIM x(-100 TO -10) AS <your_type_here>
DIM x(50 TO 100) AS <your_type_here>
DIM x(1 TO 10, 50 TO 100) AS <your_type_here>

All of the DIMs above could also be REDIM if you like for dynamic arrays.

When you declare an array with an index of 0 -> DIM x(0) <- you are actually creating an array with one value. Remember, QB64 and most other programming languages treat zero as a valid amount.

DIM x(0)
x(0) = 10

Many times I'll create dynamic arrays at the top of my code with a 0 index, such as for a ship firing bullets. As each bullet is fired I simply increase the size of the dynamic array to accommodate.

TYPE Type_Bullet
    x AS SINGLE        ' x coordinate of bullet
    y AS SINGLE        ' y coordinate of bullet
    vx AS SINGLE      ' x vector (travel)
    vy AS SINGLE      ' y vector (travel)
    Alive AS INTEGER ' is bullet still active? (true/false)
END TYPE

REDIM Bullet(0) AS Type_Bullet ' player bullet array

<later in the code>

IF PlayerFiredBullet THEN '                                     did player fire bullet?
    REDIM _PRESERVE Bullet(UBOUND(Bullet) + 1) AS Type_Bullet ' increase the size of array while preserving data already contained within
    Bullet(UBOUND(Bullet)).x = ShipX '                    apply new bullet values
    Bullet(UBOUND(Bullet)).y = ShipY
    Bullet(UBOUND(Bullet)).vx = ShipVx
    Bullet(UBOUND(Bullet)).vy = ShipVy
    Bullet(UBOUND(Bullet)).Alive = -1
END IF

Here is the link to the wiki for DIM: https://qb64phoenix.com/qb64wiki/index.php/DIM