VBA Append Function?

Is there a VBA function that performs the same task as the AutoLISP append
function?

Dale

 

Given that (append) works with LISTs, what
counterpart are you using in VBA?

If you need a list/array/vector type structure
that must be dynamically appended to frequently,
do not use arrays or REDIM PRESERVE, instead
use a Collection object.

 

Thanks Tony. I've been using arrays and REDIM PRESERVE for ages. I was just
wondering if there was a simple function to merge two arrays. I geuss I'll
research the collection object.

Best regards,

Dale

 

Like Tony said, collections are WAY easier than arrays to mess with so I'm
trying to get away from arrays all together.
However a while back I was wondering the same thing as you so here's what I
came up with.
Pretty pathetic programming but you get the idea.
only works with valid arrays at this point, haven't gotten the error
trapping worked out
and since collections are so much better, this is just a bit theoretical

Sub AppendArray(ByRef vArray As Variant, vToAdd As Variant)
Dim iStart As Integer
Dim j As Integer
If IsArray(vArray) And IsArray(vToAdd) Then
If HasUBound(vArray) And HasUBound(vToAdd) Then
iStart = UBound(vArray)

ReDim Preserve vArray((UBound(vArray) - LBound(vArray)) +
(UBound(vToAdd) - LBound(vToAdd)) + 1)
For j = LBound(vToAdd) To UBound(vToAdd)
vArray(iStart + j + 1) = vToAdd(j)
Next j
End If 'it has ubound (not an empty array)
End If 'it is an array
End Function

Function HasUBound(varArray As Variant) As Boolean
' Determines whether an array contains a ubound
'assume success
HasUBound = True
Dim lngUBound As Long
On Error Resume Next
lngUBound = UBound(varArray)
If Err.Number <> 0 Then
Err.Clear
HasUBound = False
End If
End Function


Sub test()
Dim i As Integer
Dim a1() As Integer
ReDim a1(3)

a1(0) = 1
a1(1) = 2
a1(2) = 3
a1(3) = 4

Debug.Print "A1 starts: "
For i = 0 To UBound(a1)
Debug.Print a1(i)
Next

Dim a2() As Integer
ReDim a2(3)

a2(0) = 5
a2(1) = 6
a2(2) = 7
a2(3) = 8


AppendArray a1, a2
Debug.Print "After append, A1: "
For i = 0 To UBound(a1)
Debug.Print a1(i)
Next


End Sub

 

Here is what I'm using:

' returns true if the argument array or list has been initialized
Public Function IsBounded(ArgAry As Variant) As Boolean
On Error Resume Next
IsBounded = IsNumeric(UBound(ArgAry))
End Function

' works like the AutoLISP (append expr ...) function
' appends arrays or lists together to form one array or list
' this might be changed to handle a variable number of arguments
Public Function Append(Ary1 As Variant, Ary2 As Variant) As Variant
Dim Element As Variant
Dim Index As Integer
Dim ReturnAry As Variant
If IsBounded(Ary1) And IsBounded(Ary2) Then
ReDim ReturnAry(0 To Length(Ary1) + Length(Ary2) - 1)
For Each Element In Ary1
ReturnAry(Index) = Element
Index = Index + 1
Next Element
For Each Element In Ary2
ReturnAry(Index) = Element
Index = Index + 1
Next Element
Else
MyError "Append: Arguments must both be arrays"
End If
Append = ReturnAry
End Function