How to Eliminate Code Duplication in F# When Using Discrete Types

Discover effective methods to remove code duplication in F# when handling discrete types like WordDocument and WordTableCell.
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Introduction

Code duplication can be a source of frustration for developers, especially when you're working with discrete types that share a similar API—like WordDocument and WordTableCell in F#. In this post, we will address how to effectively eliminate this duplication, leading to cleaner, more maintainable code.

Understanding the Problem

The core issue arises when we have a discrete union type, WordContainer, that can represent either a Doc (of type WordDocument) or a Cell (of type WordTableCell). Although these types have the same functions available for their APIs, there isn't a base class or interface they share. As a result, using traditional methods to unify the code can lead to verbose match expressions and redundant code, making it difficult to keep your codebase DRY (Don't Repeat Yourself).

Solutions to Eliminate Code Duplication

Solution 1: Helper Functions

One of the simplest ways to overcome this problem is to create helper functions that factor out the duplicated logic. By doing this, you can call the appropriate functions based on which type you are dealing with, rather than maintaining separate implementations in each branch of your match expressions.

Implementing the Helper Function

You can define a unified helper function called addPartUnified like this:

[[See Video to Reveal this Text or Code Snippet]]

Calling the Unified Function

To call this unified function, use the following pattern:

[[See Video to Reveal this Text or Code Snippet]]

This method essentially simulates a type class in F#, streamlining your function calls and encouraging reuse.

Solution 2: Adding Members

Another approach you can take is to extend the WordContainer type by adding member functions for AddParagraph and AddTable. This method creates a more organized structure, making it easier to manage changes in the future.

Adding Members to WordContainer

Define your WordContainer with members as follows:

[[See Video to Reveal this Text or Code Snippet]]

Utilizing the New Members

Now, you can refactor your addPart function to utilize these new members:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing either of the two solutions discussed—using helper functions or adding members to your types—you can significantly reduce code duplication in your F# applications. This not only enhances readability and maintainability but also contributes to a more robust codebase overall.

With these approaches, you'll be well on your way to writing cleaner, more efficient F# code while handling discrete types effectively.