lbound - Arrays - VB6Parse Library Reference

LBound Function

Returns a Long containing the smallest available subscript for the indicated dimension of an array.

Syntax

LBound(arrayname, [dimension])

Parameters

arrayname (Required): Name of the array variable
dimension (Optional): Integer specifying which dimension's lower bound to return
If omitted, defaults to 1 (first dimension)
Must be between 1 and the number of dimensions in the array

Return Value

Returns a Long of the smallest available subscript for the specified dimension.
By default, arrays start at 0 unless Option Base 1 is specified.
Returns 0 for standard arrays (Option Base 0).
Returns 1 for arrays when Option Base 1 is specified.
For arrays declared with explicit bounds, returns the specified lower bound.
Dynamic arrays preserve their lower bound across ReDim operations.

Remarks

The LBound function is essential for array processing: - Returns the lower bound (minimum index) of an array dimension - Counterpart to UBound (which returns upper bound) - Critical for correctly iterating through arrays - Default lower bound is 0 (unless Option Base 1) - Can specify explicit lower bounds:

Dim arr(5 To 10) 'LBound = 5

Works with multi-dimensional arrays using dimension parameter
Omitting dimension parameter returns bound of first dimension
Dynamic arrays must be dimensioned before calling LBound
Fixed-size arrays always have bounds available
ParamArray parameters always have an LBound value of 0.
Essential for writing dimension-agnostic code
Use with UBound to determine array size = UBound - LBound + 1
Safer than assuming arrays start at 0
ReDim Preserve maintains lower bounds
Common in For loops:

For i = LBound(arr) To UBound(arr)
Next

Common Errors

Error 9 (Subscript out of range): If dimension exceeds array dimensions
Error 9 (Subscript out of range): If array has not been dimensioned (for dynamic arrays)

Performance Considerations

Fast Operation: LBound is a very fast intrinsic function
No Overhead: Direct access to array metadata
Cache Results: If using in loops, cache LBound/UBound values
Bounds in Loops: Better to cache than call repeatedly

Performance Optimization

Less efficient - Calls `LBound` Every Iteration

For i = LBound(arr) To UBound(arr)
    ' process arr(i)
Next i

More Efficient For Very Large Loops

Dim lb As Long, ub As Long
lb = LBound(arr)
ub = UBound(arr)
For i = lb To ub
    ' process arr(i)
Next i

Typical Uses

Array Iteration: Loop through arrays with correct starting index
Array Size Calculation: Determine number of elements
Bounds Validation: Check if index is within valid range
Array Copying: Copy elements with proper bounds
Multi-dimensional Arrays: Access correct dimension bounds
Dynamic Arrays: Verify array has been dimensioned
Generic Functions: Write functions that work with any array bounds
Option Base Handling: Code that works regardless of Option Base setting

Limitations

Cannot modify array bounds (use ReDim for that)
Raises error for undimensioned dynamic arrays
Dimension parameter must be valid (1 to number of dimensions)
Cannot determine if array is fixed-size or dynamic
No way to get all bounds at once (must call separately for each dimension)

Platform and Version Notes

Available in all VB6 versions
Part of VBA core functions
Returns Long type
Works with all array types (Variant, typed, object arrays)
ReDim Preserve maintains lower bounds
ParamArray always has LBound = 0

UBound: Get upper bound of array dimension
IsArray: Check if variable is an array
ReDim: Redimension dynamic array
Array: Create Variant array
Split: Create array from delimited string

Function	Purpose	Returns	Use Case
`LBound`	Get lower bound	`Long`	Minimum valid index
`UBound`	Get upper bound	`Long`	Maximum valid index
`IsArray`	Check if array	`Boolean`	Validate array type
`Array`	Create array	`Variant`	Initialize arrays
`ReDim`	Resize array	N/A	Dynamic array sizing

Best Practices

Always Use LBound: Don't assume arrays start at 0
Dimension Parameter: Specify dimension for multi-dimensional arrays
Error Handling: Handle undimensioned dynamic arrays
Array Size: Use UBound - LBound + 1 for element count
Cache Values: Store LBound/UBound in variables for repeated use
Generic Code: Write functions that work with any array bounds
Validate Bounds: Check if indices are within LBound to UBound range
Document Assumptions: Note expected array bounds in comments

`LBound` and `Option Base`

Option Base 0 (default)

Dim arr1(5) As Integer
Debug.Print LBound(arr1)         ' 0
Debug.Print UBound(arr1)         ' 5

Option Base 1

Option Base 1
Dim arr2(5) As Integer
Debug.Print LBound(arr2)         ' 1
Debug.Print UBound(arr2)         ' 5

Explicit Bounds (Overrides Option Base)

Dim arr3(10 To 20) As Integer
Debug.Print LBound(arr3)         ' 10
Debug.Print UBound(arr3)         ' 20

Array Size Calculation

' Correct way to get array size
Function GetArraySize(arr As Variant) As Long
    If Not IsArray(arr) Then
        GetArraySize = 0
    Else
        GetArraySize = UBound(arr) - LBound(arr) + 1
    End If
End Function
' Examples
Dim a(0 To 10) As Integer       ' Size = 11
Dim b(1 To 10) As Integer       ' Size = 10
Dim c(5 To 15) As Integer       ' Size = 11
Debug.Print GetArraySize(a)     ' 11
Debug.Print GetArraySize(b)     ' 10
Debug.Print GetArraySize(c)     ' 11

Examples

Example 1: Basic Array Iteration

Dim arr(5) As Integer
Dim i As Long
For i = LBound(arr) To UBound(arr)
    arr(i) = i * 2
Next i

Example 2: Explicit Lower Bound

Dim months(1 To 12) As String
Debug.Print LBound(months)           ' 1
Debug.Print UBound(months)           ' 12

Example 3: Multi-Dimensional Array

Dim grid(1 To 10, 1 To 20) As Integer
Debug.Print LBound(grid, 1)          ' 1 - first dimension
Debug.Print LBound(grid, 2)          ' 1 - second dimension
Debug.Print LBound(grid)             ' 1 - defaults to first dimension

Example 4: Calculate Array Size

Dim values(10 To 50) As Double
Dim size As Long
size = UBound(values) - LBound(values) + 1
Debug.Print size                     ' 41 elements

Common Patterns

Pattern 1: Safe Array Iteration

Sub ProcessArray(arr As Variant)
    Dim i As Long
    If Not IsArray(arr) Then Exit Sub
    For i = LBound(arr) To UBound(arr)
        Debug.Print arr(i)
    Next i
End Sub

Pattern 2: Array Size Function

Function ArraySize(arr As Variant, Optional dimension As Long = 1) As Long
    If Not IsArray(arr) Then
        ArraySize = 0
    Else
        ArraySize = UBound(arr, dimension) - LBound(arr, dimension) + 1
    End If
End Function

Pattern 3: Copy Array With Correct Bounds

Function CopyArray(source As Variant) As Variant
    Dim dest As Variant
    Dim i As Long
    If Not IsArray(source) Then Exit Function
    ReDim dest(LBound(source) To UBound(source))
    For i = LBound(source) To UBound(source)
        If IsObject(source(i)) Then
            Set dest(i) = source(i)
        Else
            dest(i) = source(i)
        End If
    Next i
    CopyArray = dest
End Function

Pattern 4: Check If Array Is Empty

Function IsArrayEmpty(arr As Variant) As Boolean
    On Error Resume Next
    IsArrayEmpty = (UBound(arr) < LBound(arr))
    If Err.Number <> 0 Then IsArrayEmpty = True
    On Error GoTo 0
End Function

Pattern 5: Array Contains Value

Function ArrayContains(arr As Variant, value As Variant) As Boolean
    Dim i As Long
    If Not IsArray(arr) Then Exit Function
    For i = LBound(arr) To UBound(arr)
        If arr(i) = value Then
            ArrayContains = True
            Exit Function
        End If
    Next i
    ArrayContains = False
End Function

Pattern 6: Find Element Index

Function FindInArray(arr As Variant, value As Variant) As Long
    Dim i As Long
    FindInArray = -1  ' Not found
    If Not IsArray(arr) Then Exit Function
    For i = LBound(arr) To UBound(arr)
        If arr(i) = value Then
            FindInArray = i
            Exit Function
        End If
    Next i
End Function

Pattern 7: Reverse Array In Place

Sub ReverseArray(arr As Variant)
    Dim i As Long
    Dim j As Long
    Dim temp As Variant
    If Not IsArray(arr) Then Exit Sub
    i = LBound(arr)
    j = UBound(arr)
    Do While i < j
        temp = arr(i)
        arr(i) = arr(j)
        arr(j) = temp
        i = i + 1
        j = j - 1
    Loop
End Sub

Pattern 8: Slice Array

Function SliceArray(arr As Variant, startIndex As Long, endIndex As Long) As Variant
    Dim result() As Variant
    Dim i As Long
    Dim j As Long
    If Not IsArray(arr) Then Exit Function
    If startIndex < LBound(arr) Or endIndex > UBound(arr) Then Exit Function
    ReDim result(0 To endIndex - startIndex)
    j = 0
    For i = startIndex To endIndex
        result(j) = arr(i)
        j = j + 1
    Next i
    SliceArray = result
End Function

Pattern 9: Fill Array With Value

Sub FillArray(arr As Variant, value As Variant)
    Dim i As Long
    If Not IsArray(arr) Then Exit Sub
    For i = LBound(arr) To UBound(arr)
        If IsObject(value) Then
            Set arr(i) = value
        Else
            arr(i) = value
        End If
    Next i
End Sub

Pattern 10: Multi-Dimensional Array Iteration

Sub ProcessGrid(grid As Variant)
    Dim i As Long, j As Long
    If Not IsArray(grid) Then Exit Sub
    For i = LBound(grid, 1) To UBound(grid, 1)
        For j = LBound(grid, 2) To UBound(grid, 2)
            Debug.Print grid(i, j)
        Next j
    Next i
End Sub

Advanced Usage Examples

Example 1: Generic Array Utilities Class

Public Class ArrayUtils
    Public Function GetSize(arr As Variant, Optional dimension As Long = 1) As Long
        On Error GoTo ErrorHandler
        If Not IsArray(arr) Then
            GetSize = 0
        Else
            GetSize = UBound(arr, dimension) - LBound(arr, dimension) + 1
        End If
        Exit Function
    ErrorHandler:
        GetSize = 0
    End Function
    Public Function Clone(source As Variant) As Variant
        Dim dest As Variant
        Dim i As Long
        If Not IsArray(source) Then Exit Function
        ReDim dest(LBound(source) To UBound(source))
        For i = LBound(source) To UBound(source)
            If IsObject(source(i)) Then
                Set dest(i) = source(i)
            Else
                dest(i) = source(i)
            End If
        Next i
        Clone = dest
    End Function
    Public Function IndexOf(arr As Variant, value As Variant) As Long
        Dim i As Long
        IndexOf = -1
        If Not IsArray(arr) Then Exit Function
        For i = LBound(arr) To UBound(arr)
            If arr(i) = value Then
                IndexOf = i
                Exit Function
            End If
        Next i
    End Function
    Public Function Reverse(arr As Variant) As Variant
        Dim result As Variant
        Dim i As Long
        Dim j As Long
        If Not IsArray(arr) Then Exit Function
        ReDim result(LBound(arr) To UBound(arr))
        j = UBound(arr)
        For i = LBound(arr) To UBound(arr)
            result(j) = arr(i)
            j = j - 1
        Next i
        Reverse = result
    End Function
End Class

Example 2: Safe array accessor with bounds checking

Public Class SafeArray
    Private m_data As Variant
    Public Sub Initialize(size As Long, Optional lowerBound As Long = 0)
        ReDim m_data(lowerBound To lowerBound + size - 1)
    End Sub
    Public Property Get Item(index As Long) As Variant
        If index < LBound(m_data) Or index > UBound(m_data) Then
            Err.Raise 9, "SafeArray", "Index out of bounds: " & index & _
                      " (valid range: " & LBound(m_data) & " to " & UBound(m_data) & ")"
        End If
        If IsObject(m_data(index)) Then
            Set Item = m_data(index)
        Else
            Item = m_data(index)
        End If
    End Property
    Public Property Let Item(index As Long, value As Variant)
        If index < LBound(m_data) Or index > UBound(m_data) Then
            Err.Raise 9, "SafeArray", "Index out of bounds"
        End If
        If IsObject(value) Then
            Set m_data(index) = value
        Else
            m_data(index) = value
        End If
    End Property
    Public Property Get LowerBound() As Long
        LowerBound = LBound(m_data)
    End Property
    Public Property Get UpperBound() As Long
        UpperBound = UBound(m_data)
    End Property
    Public Property Get Count() As Long
        Count = UBound(m_data) - LBound(m_data) + 1
    End Property
End Class

Example 3: Matrix Operations Helper

Public Class MatrixHelper
    Public Function GetRowCount(matrix As Variant) As Long
        If Not IsArray(matrix) Then
            GetRowCount = 0
        Else
            GetRowCount = UBound(matrix, 1) - LBound(matrix, 1) + 1
        End If
    End Function
    Public Function GetColumnCount(matrix As Variant) As Long
        If Not IsArray(matrix) Then
            GetColumnCount = 0
        Else
            GetColumnCount = UBound(matrix, 2) - LBound(matrix, 2) + 1
        End If
    End Function
    Public Function GetRow(matrix As Variant, rowIndex As Long) As Variant
        Dim result() As Variant
        Dim j As Long
        Dim k As Long
        If Not IsArray(matrix) Then Exit Function
        ReDim result(LBound(matrix, 2) To UBound(matrix, 2))
        For j = LBound(matrix, 2) To UBound(matrix, 2)
            result(j) = matrix(rowIndex, j)
        Next j
        GetRow = result
    End Function
    Public Function GetColumn(matrix As Variant, colIndex As Long) As Variant
        Dim result() As Variant
        Dim i As Long
        If Not IsArray(matrix) Then Exit Function
        ReDim result(LBound(matrix, 1) To UBound(matrix, 1))
        For i = LBound(matrix, 1) To UBound(matrix, 1)
            result(i) = matrix(i, colIndex)
        Next i
        GetColumn = result
    End Function
    Public Sub Fill(matrix As Variant, value As Variant)
        Dim i As Long, j As Long
        If Not IsArray(matrix) Then Exit Sub
        For i = LBound(matrix, 1) To UBound(matrix, 1)
            For j = LBound(matrix, 2) To UBound(matrix, 2)
                matrix(i, j) = value
            Next j
        Next i
    End Sub
End Class

Example 4: Dynamic Array Manager

Public Class DynamicArray
    Private m_data() As Variant
    Private m_count As Long
    Private m_lowerBound As Long
    Private Sub Class_Initialize()
        m_count = 0
        m_lowerBound = 0
        ReDim m_data(m_lowerBound To m_lowerBound + 9)  ' Initial capacity of 10
    End Sub
    Public Sub Add(value As Variant)
        If m_count > UBound(m_data) - LBound(m_data) Then
            ' Resize array (double capacity)
            ReDim Preserve m_data(LBound(m_data) To UBound(m_data) * 2 + 1)
        End If
        If IsObject(value) Then
            Set m_data(LBound(m_data) + m_count) = value
        Else
            m_data(LBound(m_data) + m_count) = value
        End If
        m_count = m_count + 1
    End Sub
    Public Function ToArray() As Variant
        Dim result() As Variant
        Dim i As Long
        If m_count = 0 Then
            ToArray = Array()
            Exit Function
        End If
        ReDim result(m_lowerBound To m_lowerBound + m_count - 1)
        For i = 0 To m_count - 1
            If IsObject(m_data(LBound(m_data) + i)) Then
                Set result(m_lowerBound + i) = m_data(LBound(m_data) + i)
            Else
                result(m_lowerBound + i) = m_data(LBound(m_data) + i)
            End If
        Next i
        ToArray = result
    End Function
    Public Property Get Count() As Long
        Count = m_count
    End Property
    Public Property Get Capacity() As Long
        Capacity = UBound(m_data) - LBound(m_data) + 1
    End Property
End Class

Error Handling

LBound can raise errors in specific cases:

' Error 9: Subscript out of range - dimension exceeds array dimensions
Dim arr(5, 10) As Integer
' Debug.Print LBound(arr, 3)  ' Error 9 - only 2 dimensions

' Error 9: Array not dimensioned (dynamic arrays)
Dim dynArr() As String
' Debug.Print LBound(dynArr)  ' Error 9 - not dimensioned yet

' Safe pattern with error handling
Function GetLowerBound(arr As Variant, Optional dimension As Long = 1) As Long
    On Error Resume Next
    GetLowerBound = LBound(arr, dimension)
    If Err.Number <> 0 Then
        GetLowerBound = -1  ' Indicate error
    End If
    On Error GoTo 0
End Function