Typed Design Patterns for the Functional Era

07/13/2023

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by   Will Crichton, et al.

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This paper explores how design patterns could be revisited in the era of mainstream functional programming languages. I discuss the kinds of knowledge that ought to be represented as functional design patterns: architectural concepts that are relatively self-contained, but whose entirety cannot be represented as a language-level abstraction. I present four concrete examples embodying this idea: the Witness, the State Machine, the Parallel Lists, and the Registry. Each pattern is implemented in Rust to demonstrate how careful use of a sophisticated type system can better model each domain construct and thereby catch user mistakes at compile-time.