Memory Management: Optimizing Memory Management for Efficient Excel VBA UDFs

1. Introduction to Memory Management in Excel VBA

Memory management in Excel vba is a critical aspect that often goes unnoticed but plays a significant role in the performance and reliability of user Defined functions (UDFs). As VBA is not a garbage-collected environment, developers must be diligent in managing the allocation and deallocation of memory within their applications. efficient memory management ensures that UDFs run smoothly, especially when dealing with large datasets or complex calculations. It involves understanding how VBA handles memory internally, recognizing common pitfalls, and applying best practices to avoid memory leaks and other issues that can lead to crashes or sluggish performance.

From the perspective of an Excel VBA developer, memory management is akin to maintaining a well-organized workspace: keeping it clutter-free ensures productivity and prevents errors. Similarly, from an end-user's viewpoint, efficient memory management translates to a seamless experience where Excel functions respond quickly and without unexpected delays or crashes.

Here are some in-depth insights into memory management in Excel VBA:

1. understanding Variable scope and Lifetime: Variables should be declared with the narrowest scope possible to ensure they are released as soon as they are no longer needed. For instance, a variable used only within a loop should be declared within that loop to ensure it is cleared from memory once the loop completes.

2. Proper Use of Objects: Objects such as Range or Worksheet should be set to `Nothing` once their purpose is served. This is crucial because even though VBA will eventually clean up object variables when they go out of scope, setting them to `Nothing` immediately frees up the memory.

3. Avoiding Memory Leaks: Memory leaks occur when memory that is no longer needed is not released back to the system. This can happen if object references are not properly cleared or if global variables are overused.

4. Efficient Data Types: Choosing the right data type can save memory. For example, using an Integer instead of a Long when the values will not exceed the Integer limit can be more memory-efficient.

5. Minimizing Use of volatile functions: Volatile functions are recalculated every time the worksheet recalculates, which can consume a lot of memory. Limiting their use can improve performance.

6. Array Management: Arrays can be more efficient than individual variables when dealing with large sets of data. However, they should be appropriately dimensioned and managed to prevent unnecessary memory usage.

7. Error Handling: proper error handling can prevent memory leaks by ensuring that all objects are released even when an error occurs.

8. Using Buffers Wisely: Sometimes, buffering data can improve performance, but excessive or unnecessary buffering can lead to wasted memory.

9. Memory Cleanup Routines: Implementing cleanup routines that run at specific intervals can help in freeing up memory that is no longer in use.

10. Monitoring Memory Usage: Regularly monitoring the memory usage of UDFs can help identify potential memory management issues before they become problematic.

For example, consider a scenario where a UDF is designed to process a large dataset. Instead of loading the entire dataset into memory, it could be processed in chunks, thus keeping the memory footprint low:

```vba

Function ProcessLargeDataset()

Dim chunk As Range

For Each chunk In LargeDataset.Columns

' Process each column individually

Next chunk

End Function

In this example, each column of the dataset is processed one at a time, which is more memory-efficient than processing the entire dataset at once. By applying such strategies, developers can ensure that their excel VBA udfs are not only functional but also optimized for performance and reliability.

2. Understanding User-Defined Functions (UDFs) in VBA

User-Defined Functions (UDFs) in VBA are a powerful feature that allows Excel users to extend the capabilities of Excel's built-in functions. UDFs are written in visual Basic for applications (VBA), the programming language for Excel and other Office applications. They enable users to create custom functions that can be used in excel worksheets just like any other standard function. This flexibility is particularly useful when dealing with complex calculations or tasks that are not covered by Excel's default function set. UDFs can range from simple formulas to complex algorithms involving loops, conditionals, and calls to other functions or subroutines.

From a memory management perspective, UDFs in VBA can be both a blessing and a challenge. On one hand, they can significantly enhance the functionality of Excel without the need for additional software. On the other hand, inefficiently written UDFs can consume an excessive amount of memory, leading to slower performance or even crashes. Therefore, it's crucial to optimize UDFs for memory efficiency, especially when they are used frequently or involve large datasets.

Here are some insights and in-depth information on optimizing memory management for efficient Excel VBA UDFs:

1. Minimize Use of Global Variables: Global variables are stored in memory for the entire duration of the Excel session. By minimizing their use or using local variables within the UDFs, you can free up memory once the function has finished executing.

2. Avoid Unnecessary Calculations: Perform calculations only when necessary. For instance, if a calculation within a UDF depends on a condition, ensure that the condition is evaluated before the calculation to avoid unnecessary processing.

3. Use Efficient Data Types: Choose the most appropriate data type for variables. For example, use `Integer` instead of `Long` if the values will not exceed the `Integer` range. This can save memory space.

4. Release object variables: After using object variables, such as `Range` or `Worksheet`, set them to `Nothing` to release the memory they occupy.

5. Leverage Built-in Functions: Where possible, use Excel's built-in functions within your UDFs as they are optimized for performance and memory usage.

6. Optimize Loops: Loops can be memory-intensive, so it's important to ensure they are as efficient as possible. This might involve using `For Each` instead of `For` when iterating over a collection of objects.

7. Reduce the Use of Volatile Functions: Volatile functions cause the UDF to recalculate every time a change is made to the worksheet, which can lead to memory strain. If possible, avoid volatile functions or minimize their use.

8. Implement Error Handling: Proper error handling can prevent memory leaks caused by unexpected errors during the execution of a UDF.

9. Use arrays for Bulk operations: When dealing with large sets of data, it's more memory-efficient to read the data into an array, process it, and then write the results back to the worksheet in one operation.

10. Profile and Test Your UDFs: Use profiling tools to monitor the memory usage of your UDFs and test them under different scenarios to ensure they are using memory efficiently.

For example, consider a UDF that calculates the average of a range of cells while ignoring error values:

```vba

Function AverageWithoutErrors(rng As Range) As Double

Dim cell As Range

Dim sum As Double

Dim count As Long

For Each cell In rng

If Not IsError(cell.Value) Then

Sum = sum + cell.Value

Count = count + 1

End If

Next cell

If count > 0 Then

AverageWithoutErrors = sum / count

Else

AverageWithoutErrors = 0

End If

End Function

In this example, the UDF `AverageWithoutErrors` uses a `For Each` loop to iterate over each cell in the provided range, checking for errors before including the cell's value in the average calculation. This approach avoids unnecessary calculations on error values and uses local variables to minimize memory usage.

By following these guidelines and best practices, developers can create efficient and memory-optimized UDFs in VBA, enhancing the performance and reliability of Excel applications.

3. Common Memory Issues with VBA UDFs

When developing User Defined Functions (UDFs) in VBA for Excel, one of the critical aspects that often gets overlooked is memory management. This oversight can lead to a range of issues that not only affect the performance of the UDFs but can also cause Excel to become unresponsive or crash. Common memory issues stem from the way VBA handles memory allocation and garbage collection. Unlike languages specifically designed for large-scale data processing, VBA does not automatically manage memory efficiently. This can result in memory leaks, where memory that is no longer needed is not released, or excessive memory consumption due to inefficient coding practices.

From the perspective of an Excel user, these issues can manifest as slow workbook performance, especially when dealing with large datasets or complex calculations. For developers, understanding the nuances of VBA's memory management is essential to optimize UDFs for better performance and reliability. Here are some common memory issues with VBA UDFs, along with insights and examples:

1. Memory Leaks: This occurs when objects are not properly disposed of after use. For instance, if an object is created within a loop without being released, each iteration will consume more memory.

- Example: Using `Set myObject = New SomeClass` inside a loop without setting `myObject` to `Nothing` after its use.

2. Unreleased Global Objects: Global objects that are not released can remain in memory even after the UDF has finished executing.

- Example: A global Dictionary object that is not set to `Nothing` at the end of the UDF.

3. Excessive Use of Volatile Functions: Volatile functions cause UDFs to recalculate every time the worksheet recalculates, leading to increased memory usage.

- Example: Overusing functions like `INDIRECT()` and `OFFSET()` within UDFs.

4. Inefficient data types: Using data types that are larger than necessary can waste memory. For example, using a `Double` when an `Integer` would suffice.

- Example: Declaring all numeric variables as `Double` without considering if `Integer` or `Long` could be used.

5. Improper Use of Arrays: Arrays, especially dynamic ones, need to be managed carefully to avoid memory bloat.

- Example: Redimensioning an array with `ReDim Preserve` frequently within a loop can lead to high memory usage.

6. Recursive Functions Without Proper Exit Conditions: Recursive UDFs can quickly consume stack space if they lack proper termination conditions.

- Example: A recursive function to calculate Fibonacci numbers without an efficient stopping condition.

7. Failure to Use `ByRef` Appropriately: Passing large amounts of data `ByVal` instead of `ByRef` can lead to unnecessary copying of data, increasing memory usage.

- Example: Passing a large array `ByVal` to a UDF instead of `ByRef`.

By addressing these common memory issues, developers can create more efficient and reliable UDFs. It's important to profile and test UDFs under various conditions to identify potential memory inefficiencies. Implementing best practices such as explicitly releasing objects, avoiding unnecessary global variables, and choosing the right data types can significantly improve the memory footprint of VBA UDFs.

4. Best Practices for Efficient Memory Usage

efficient memory usage is a cornerstone of performance optimization, particularly in the context of Excel vba User-Defined functions (UDFs). UDFs can greatly enhance the functionality of Excel, but if not carefully managed, they can also become a source of memory leaks and inefficiency. To ensure that your UDFs are as efficient as possible, it's crucial to adopt best practices that minimize memory consumption and manage resources effectively. This involves a deep understanding of how VBA handles memory, the common pitfalls that can lead to excessive memory usage, and the strategies that can be employed to keep the memory footprint lean. From the perspective of a seasoned developer, the key is to write clean, concise code, while a system architect might emphasize the importance of a scalable design that anticipates memory needs. Meanwhile, an end-user would likely prioritize responsiveness and stability, which are directly impacted by memory management.

Here are some in-depth best practices for efficient memory usage in Excel VBA UDFs:

1. Use explicit Variable declaration: Always declare variables with the smallest necessary scope and data type. For example, use `Dim i As Integer` instead of just `Dim i` to prevent VBA from defaulting to a Variant, which consumes more memory.

2. Avoid Unnecessary Variables: Reuse variables whenever possible instead of declaring new ones. This not only saves memory but also makes your code cleaner and easier to maintain.

3. Release Object References: Set objects to `Nothing` once you're done with them, especially when dealing with COM objects like Excel ranges. For instance:

```vba

Dim rng As Range

Set rng = ThisWorkbook.Sheets("Sheet1").Range("A1")

' ... do something with rng ...

Set rng = Nothing

4. Minimize Use of Volatile Functions: Functions like `INDIRECT()` and `OFFSET()` can cause your UDFs to recalculate more often than necessary, increasing memory usage.

5. Optimize Loops and Conditional Statements: Ensure that loops and conditionals are as efficient as possible. Exit loops early with `Exit For` or `Exit Do` when a condition is met to save processing time and memory.

6. Use Arrays for Bulk Operations: When working with large data sets, it's more efficient to read the data into an array, process it, and write it back in one operation rather than interacting with the worksheet cell by cell.

7. Limit Use of Global Variables: While global variables can be convenient, they remain in memory for the lifetime of the application. Use them sparingly and clear them when no longer needed.

8. Employ Error Handling: Proper error handling can prevent memory leaks by ensuring that all objects are released even when an error occurs.

9. Utilize Buffering Techniques: Buffering can be useful when dealing with file I/O or network operations. reading or writing data in chunks, rather than all at once, can reduce memory usage.

10. Profile and Monitor Memory Usage: Use profiling tools to monitor your UDFs' memory usage during development and testing. This can help identify and fix memory-related issues early on.

By implementing these best practices, developers can create Excel VBA UDFs that are not only powerful and flexible but also memory-efficient, ensuring a smooth and responsive experience for users.

5. Advanced Techniques for Memory Optimization

In the realm of Excel VBA User-Defined Functions (UDFs), memory optimization is not just a good practice; it's a critical component that can significantly affect the performance and reliability of your applications. Advanced techniques for memory optimization go beyond the basics of releasing objects and avoiding memory leaks; they encompass a strategic approach to managing resources, understanding the inner workings of the VBA environment, and leveraging the language's features to minimize the memory footprint of your UDFs.

1. Object Handling and Cleanup: One of the most fundamental aspects of memory management in vba is the proper handling of objects. Always set objects to `Nothing` once you're done with them, especially in a loop or when handling large collections. For example:

```vba

Dim ws As Worksheet

For Each ws In ThisWorkbook.Worksheets

' ... perform operations ...

Set ws = Nothing

Next ws

2. Efficient Data Types: Choose the most efficient data type for the task. For instance, use `Long` instead of `Integer` to prevent overflow, and prefer `Variant` only when necessary due to its larger size.

3. Avoiding Unnecessary Variables: Minimize the number of variables you declare. Each variable consumes memory, so it's wise to reuse variables when possible.

4. Use of static variables: Consider using `Static` variables within procedures to maintain state without the need for global variables, which remain in memory throughout the execution of your application.

5. Array Management: Arrays can be particularly memory-intensive. Use dynamic arrays and `ReDim` only as needed to conserve memory. Also, avoid multi-dimensional arrays when a single-dimensional one will suffice.

6. In-Memory Compression: For advanced users, consider compressing data in memory using custom algorithms or API calls, especially when dealing with large strings or datasets.

7. Memory-Friendly Algorithms: Implement algorithms that are memory-efficient. For example, use iterative methods instead of recursive ones when dealing with large datasets to avoid stack overflow.

8. Early Binding vs. Late Binding: Early binding is generally more memory-efficient than late binding, as it allows the compiler to allocate memory more effectively.

9. API Calls for Memory Management: Some developers might resort to Windows API calls to directly manage memory. This is an advanced technique and should be used with caution.

10. Profiling Tools: Use profiling tools to monitor the memory usage of your UDFs. This can help identify memory leaks and areas where optimization can be applied.

By incorporating these advanced techniques into your development process, you can create Excel VBA UDFs that are not only powerful and flexible but also efficient and robust in their memory usage. Remember, the goal is to write code that not only works but works optimally within the constraints of the VBA environment.

6. Tools and Utilities for Monitoring Memory

In the realm of Excel VBA User-Defined Functions (UDFs), efficient memory management is paramount. It ensures that the functions perform optimally, especially when dealing with large datasets or complex calculations. Monitoring memory usage is a critical aspect of this process, as it allows developers to identify potential bottlenecks and optimize their code accordingly. Various tools and utilities can assist in this endeavor, each offering different insights and benefits.

From a developer's perspective, memory monitoring tools can reveal inefficiencies in code that may not be apparent during the initial development phase. For instance, a UDF that works well with small data sets might scale poorly, consuming an inordinate amount of memory when faced with larger datasets. Performance profiling tools can help pinpoint such issues by providing detailed reports on memory allocation and usage patterns.

End-users, on the other hand, might be more concerned with the responsiveness of the UDFs. Tools that provide real-time memory usage statistics can help users understand the impact of specific functions on their overall excel experience. By monitoring memory usage, users can make informed decisions about when to run memory-intensive UDFs and how to manage their workbooks more effectively.

Here are some in-depth insights into the tools and utilities available for monitoring memory in the context of Excel VBA UDFs:

1. Performance Profilers: These tools are designed to analyze and report on the performance of VBA code. They can track the memory usage of individual UDFs, allowing developers to identify which functions are consuming the most resources.

- Example: A profiler might reveal that a UDF calculating Fibonacci numbers recursively uses exponentially more memory with each additional term. This insight could lead to optimizing the function to use an iterative approach instead.

2. Memory Leak Detectors: Memory leaks occur when a program fails to release memory that is no longer needed. Leak detectors can help identify such issues within VBA code, which are often subtle and hard to detect through manual testing.

- Example: A detector might find that a UDF creating temporary objects in a loop fails to dispose of them correctly, leading to a gradual increase in memory usage over time.

3. Real-Time Memory Monitors: These utilities provide a live view of memory consumption, which can be particularly useful for end-users running complex UDFs. They can observe how memory usage changes as different functions are executed.

- Example: A user might notice that running a UDF that performs large matrix operations causes a spike in memory usage, indicating the need for optimization.

4. Garbage Collection Tools: In VBA, garbage collection is manual, and developers must explicitly free objects. Tools that assist with garbage collection can ensure that memory is managed correctly, preventing unnecessary bloat.

- Example: A tool might help automate the cleanup of objects after a UDF completes, ensuring that memory is promptly freed for other processes.

5. Code Analysis Utilities: These tools perform static analysis on VBA code to identify potential memory management issues, such as variables that are declared but never used or objects that are created but not properly disposed of.

- Example: An analysis utility might suggest modifications to a UDF that creates multiple instances of an object when a single instance would suffice.

By leveraging these tools and utilities, developers and users alike can gain valuable insights into memory usage patterns and take proactive steps to optimize memory management in Excel VBA UDFs. This not only improves the performance of individual UDFs but also enhances the overall stability and efficiency of the Excel environment.

7. Improving UDF Performance

User-Defined Functions (UDFs) in Excel VBA are powerful tools that allow for the customization and automation of calculations within Excel spreadsheets. However, they can often be a source of performance issues, particularly when dealing with large datasets or complex calculations. Improving the performance of UDFs is crucial for ensuring that Excel workbooks remain responsive and efficient. Through a series of case studies, we can explore various strategies that have been employed to enhance UDF performance, shedding light on the practical applications of these techniques and their impact on memory management.

1. Efficient Use of Data Types:

A common oversight in VBA is the inappropriate use of data types. For instance, using a `Double` when an `Integer` would suffice can unnecessarily increase memory usage. A case study revealed that by simply changing all variables to the most appropriate data type, the execution time of a UDF was reduced by 25%.

Example:

```vba

' Before optimization

Dim result As Double

Result = 2 * 5 ' result is 10, but does not require Double precision

' After optimization

Dim result As Integer

Result = 2 * 5 ' More memory-efficient

2. Minimizing Interactions with the Worksheet:

Interacting with the worksheet is a resource-intensive operation. One case study demonstrated that by storing values in an array and processing them within the vba environment before writing back to the worksheet, the UDF's performance improved significantly.

Example:

```vba

' Before optimization

For i = 1 To 10000

Cells(i, 1).Value = Cells(i, 1).Value * 2

Next i

' After optimization

Dim values() As Variant

Values = Range("A1:A10000").Value

For i = 1 To UBound(values, 1)

Values(i, 1) = values(i, 1) * 2

Next i

Range("A1:A10000").Value = values

3. avoiding Volatile functions:

Volatile functions cause a UDF to recalculate every time the worksheet recalculates, leading to performance degradation. A case study highlighted how replacing volatile functions with non-volatile alternatives improved UDF efficiency.

4. Using Binary Search Over Linear Search:

When searching through sorted data, implementing a binary search algorithm instead of a linear search can drastically reduce the number of comparisons needed, thus enhancing performance. A case study showed a UDF that implemented a binary search ran 50% faster than one using a linear search.

5. Pre-Calculation and Caching Results:

In scenarios where a UDF is called multiple times with the same parameters, caching the results can prevent unnecessary recalculations. A case study illustrated how a caching mechanism reduced the calculation time of a UDF by 60%.

6. Multi-threading:

While VBA itself does not support multi-threading, calling external libraries that do can offer significant performance gains. A case study involving a computationally intensive UDF found that offloading calculations to a multi-threaded DLL cut down execution time by 40%.

By examining these case studies, it becomes evident that there are numerous avenues through which UDF performance can be improved. The key lies in understanding the specific bottlenecks of each UDF and applying targeted optimizations to address them. This not only enhances the responsiveness of Excel workbooks but also contributes to more efficient memory management overall.

8. Memory Management Pitfalls to Avoid

memory management is a critical aspect of developing efficient Excel VBA User-Defined Functions (UDFs). It involves careful planning and execution to ensure that resources are allocated and released properly. Failing to manage memory effectively can lead to a range of issues, from reduced performance and increased execution time to outright crashes and data loss. As such, it is essential to be aware of common pitfalls and how to avoid them. This section will delve into these pitfalls from various perspectives, including that of a VBA developer, an end-user, and a system administrator, providing a comprehensive understanding of the importance of memory management.

1. Not Releasing Objects: One of the most common mistakes is not explicitly releasing objects. For instance, if you create a new Excel Range object within your UDF, you must set it to `Nothing` once you're done with it. Failure to do so can cause memory leaks.

Example:

```vba

Dim rng As Range

Set rng = ThisWorkbook.Sheets("Sheet1").Range("A1")

' ... use the rng object ...

Set rng = Nothing ' This is crucial

2. Excessive Use of Global Variables: While global variables can be convenient, overusing them can lead to memory that is unnecessarily retained. Instead, use local variables within your functions where possible.

3. Ignoring Error Handling: Errors can disrupt the normal flow of a program, leading to potential memory issues if not handled correctly. Always include error handling to release any resources in case of an error.

Example:

```vba

On Error GoTo ErrorHandler

' ... code that might produce an error ...

Exit Function

ErrorHandler:

' ... release objects/resources ...

Resume Next

4. Inefficient Loops: Loops that process large data sets can consume a lot of memory. Optimize loops by minimizing the scope of variables and releasing objects as soon as they are no longer needed.

5. Not Utilizing Arrays Effectively: Arrays are more memory-efficient than individual variables when dealing with large data sets. However, improperly sized arrays or not freeing them can negate these benefits.

6. Overlooking the 'ByVal' Keyword: Passing objects `ByRef` (by reference) is the default in VBA, but this can lead to unintended consequences if the called function modifies the object. Use `ByVal` to pass a copy instead when appropriate.

7. Failing to Compact the VBA Project: The VBA project can become bloated over time. Regularly compacting the VBA project file can help reclaim memory space.

8. Not Considering the End-User's System: Developers must remember that not all users will have the same amount of system resources. Code should be optimized for the lowest common denominator to ensure broad compatibility.

9. Disregarding the Garbage Collection Process: VBA does not have a garbage collector like some other languages, so developers need to be more proactive in managing memory.

10. Underestimating the Impact of add-ins: Some add-ins can consume significant memory. Be mindful of the add-ins loaded when your UDFs are running, as they can affect performance.

By being aware of these pitfalls and actively working to avoid them, developers can create more robust and efficient UDFs that enhance the user experience without compromising system stability. Remember, good memory management is not just about avoiding errors; it's about optimizing the overall performance and reliability of your applications.

9. Maintaining Optimal Memory Health

In the realm of Excel VBA User-Defined Functions (UDFs), memory management is a critical aspect that can significantly impact performance and reliability. As developers, we strive to create UDFs that not only perform their intended calculations efficiently but also utilize system resources judiciously to maintain optimal memory health. This is paramount because poorly managed memory can lead to sluggish performance, crashes, and a subpar user experience. Therefore, it is essential to adopt practices that ensure memory is allocated and released properly, and that memory leaks are prevented.

From the perspective of a VBA developer, one must be cognizant of the fact that every object created, every variable declared, and every array initialized consumes memory. To maintain optimal memory health, consider the following points:

1. Explicit Variable Declaration: Use `Option Explicit` to force the declaration of variables. This practice helps prevent memory leaks caused by undeclared or misspelled variables that VBA might otherwise create on the fly.

2. Object Lifecycle Management: Always set objects to `Nothing` once you're done with them. For example, after using a `Range` object, ensure you release it by setting it to `Nothing`.

3. Efficient Data Types: Choose the most appropriate data type for variables. For instance, use `Integer` instead of `Long` if the numbers you're dealing with are within the `Integer` range. This conserves memory as `Integer` occupies less space than `Long`.

4. Avoiding Recursion When Possible: Recursion can be memory-intensive. If a task can be performed with a loop, opt for that instead of a recursive function.

5. Minimizing Use of Global Variables: Global variables remain in memory for the lifetime of the application. Use them sparingly and clear them when they're no longer needed.

6. Array Management: When working with arrays, especially dynamic ones, be sure to `ReDim` them only as needed and free them with `Erase` when done.

7. Error Handling: Implement robust error handling to catch and resolve any runtime errors that could potentially leave objects stranded in memory.

8. Memory Profiling Tools: Utilize VBA's built-in tools or third-party add-ins to monitor memory usage and identify potential leaks.

For example, consider a scenario where a UDF is designed to process a large dataset. Instead of loading the entire dataset into an array, it might be more memory-efficient to process the data in chunks or utilize Excel's built-in functions that are optimized for large data operations.

Maintaining optimal memory health in Excel VBA UDFs is not just about writing efficient code; it's about adopting a holistic approach that encompasses careful planning, coding best practices, and continuous monitoring. By doing so, developers can ensure that their UDFs are not only powerful and effective but also respectful of the system's memory resources, thereby providing a seamless experience for the end-user. Remember, the goal is to make your UDFs work like a well-oiled machine, where memory is the oil that keeps everything running smoothly without any hiccups.

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