Possibilities of abstractions

The article compares several ways to build types with different implementations while hiding details from consumers. It focuses on F# and contrasts succinct function-record styles with interfaces, then notes other options such as passing functions directly or using discriminated unions.

Reading notes

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• Function records are a concise way to package behavior, but they do not support named parameters directly, and optional parameters need option values.
• Record fields can carry /// documentation, and record-like parameter objects can make meanings more explicit.
• Interfaces feel more natural for C#-style contracts, support named and optional parameters, and make it easier to keep state inside the implementation.
• Interface-based code can use XML documentation, which is useful when the code is consumed by other .NET libraries.
• Another option is to pass the needed functions one by one, or to turn those functions into type aliases and mix them with records.
• Discriminated unions can represent real and fake implementations, but each function must know which implementation it is using.
• The article concludes that there are no winners or losers, and that the preferred path is to start with functions and data and move toward a more OO solution only when control or state becomes necessary.