VBA (Excel) Initialize Entire Array without Looping

Question

I am fairly new to VBA, so this may be a simple question but here goes.

I would like to initialize an entire array myArray, say of integers, in VBA. I know that I can do this by a simple initialization like so:

Dim myArray
myArray = Array(1, 2, 4, 8)

But if the array is large this is cumbersome, and I'd like to initialize all of the elements to the same value. Ideally it would be something like this:

myArray(:) = 0

I tried that but the compiler complained. Then I tried myArray() = 0 and it complained about that, too.

Can anyone explain how to do this, without looping? I'd like to do it in one statement if possible.

Clarification:

I want to initialize every single element of the array to some initial value. So if I have an array Dim myArray(300) As Integer of 300 integers, for example, all 300 elements would hold the same initial value (say, the number 13).

More Clarification

I found this answer that states that you can do this with a variable like so:

Dim x As Double: x = 0

Perhaps there is a way to update the syntax slightly to make it applicable to arrays?

question from:https://stackoverflow.com/questions/19336987/vba-excel-initialize-entire-array-without-looping

Answer 1

This is easy, at least if you want a 1-based, 1D or 2D variant array:

Sub StuffVArr()
    Dim v() As Variant
    Dim q() As Variant
    v = Evaluate("=IF(ISERROR(A1:K1), 13, 13)")
    q = Evaluate("=IF(ISERROR(A1:G48), 13, 13)")
End Sub

Byte arrays also aren't too bad:

Private Declare Sub FillMemory Lib "kernel32" Alias "RtlFillMemory" _
        (dest As Any, ByVal size As Long, ByVal fill As Byte)

Sub StuffBArr()
    Dim i(0 To 39) As Byte
    Dim j(1 To 2, 5 To 29, 2 To 6) As Byte
    FillMemory i(0), 40, 13
    FillMemory j(1, 5, 2), 2 * 25 * 5, 13
End Sub

You can use the same method to fill arrays of other numeric data types, but you're limited to only values which can be represented with a single repeating byte:

Sub StuffNArrs()
    Dim i(0 To 4) As Long
    Dim j(0 To 4) As Integer
    Dim u(0 To 4) As Currency
    Dim f(0 To 4) As Single
    Dim g(0 To 4) As Double

    FillMemory i(0), 5 * LenB(i(0)), &HFF 'gives -1
    FillMemory i(0), 5 * LenB(i(0)), &H80 'gives -2139062144
    FillMemory i(0), 5 * LenB(i(0)), &H7F 'gives 2139062143

    FillMemory j(0), 5 * LenB(j(0)), &HFF 'gives -1

    FillMemory u(0), 5 * LenB(u(0)), &HFF 'gives -0.0001

    FillMemory f(0), 5 * LenB(f(0)), &HFF 'gives -1.#QNAN
    FillMemory f(0), 5 * LenB(f(0)), &H80 'gives -1.18e-38
    FillMemory f(0), 5 * LenB(f(0)), &H7F 'gives 3.40e+38

    FillMemory g(0), 5 * LenB(g(0)), &HFF 'gives -1.#QNAN
End Sub

If you want to avoid a loop in other situations, it gets even hairier. Not really worth it unless your array is 50K entries or larger. Just set each value in a loop and you'll be fast enough, as I talked about in an earlier answer.