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

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



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