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

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) has ```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 ```LBound = 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)```

## Typical Uses

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

## Basic Usage Examples

vb ' 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

vb ' 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

vb ' 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:

vb ' 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


## 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:

vb ' 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


## Best Practices

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

## Comparison with Related Functions

| 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 |

## `LBound` and `Option Base`

vb ' 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

vb ' 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 ```

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

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)

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

LBound Function

Syntax

Parameters

Return Value

Remarks

Platform and Version Notes

Limitations

Related Functions

`LBound` Function