https://blog.rafaelfernandez.dev/tags/design-patterns/ Recent content in Design-Patterns on Home Hugo -- gohugo.io en © 2026 Rafael Fernandez Sun, 22 Mar 2026 00:00:00 +0000 https://blog.rafaelfernandez.dev/posts/the-elm-architecture-a-loop-that-fits-in-your-head/ Sun, 22 Mar 2026 00:00:00 +0000 https://blog.rafaelfernandez.dev/posts/the-elm-architecture-a-loop-that-fits-in-your-head/ Model, Update, View. Three pieces, one loop, zero surprises. We explain The Elm Architecture from scratch with side-by-side examples in Rust and Scala, trace where the pattern came from, why it keeps showing up in TUIs and functional codebases, and when it stops being the right tool. https://blog.rafaelfernandez.dev/posts/tagless-final-is-denotational-semantics/ Tue, 03 Mar 2026 00:00:00 +0000 https://blog.rafaelfernandez.dev/posts/tagless-final-is-denotational-semantics/ Every trait in your hexagonal architecture is a tagless-final algebra. Every impl is an interpreter. You have been writing denotational semantics without knowing it. We trace the connection from Kiselyov’s paper through Scala’s Cats-Effect to Rust’s port traits, and show why the pattern that academics call ‘finally tagless’ is the same pattern that practitioners call ‘dependency injection.’ https://blog.rafaelfernandez.dev/posts/syntax-and-semantics-3-the-expression-problem/ Sat, 07 Feb 2026 00:00:00 +0000 https://blog.rafaelfernandez.dev/posts/syntax-and-semantics-3-the-expression-problem/ Adding a new type is easy in OOP, hard in FP. Adding a new operation is easy in FP, hard in OOP. Philip Wadler named this the Expression Problem in 1998. We show how it manifests in Rust and Scala, and tease the resolution.