https://blog.rafaelfernandez.dev/tags/tagless-final/ Recent content in Tagless-Final on Home Hugo -- gohugo.io en © 2026 Rafael Fernandez Thu, 26 Mar 2026 00:00:00 +0000 https://blog.rafaelfernandez.dev/posts/criteria4s-1-write-your-filters-once-run-them-everywhere/ Thu, 26 Mar 2026 00:00:00 +0000 https://blog.rafaelfernandez.dev/posts/criteria4s-1-write-your-filters-once-run-them-everywhere/ Write a predicate once and run it against SQL, MongoDB, Elasticsearch, or any backend. An introduction to criteria4s and its practical take on the Expression Problem. https://blog.rafaelfernandez.dev/posts/criteria4s-1-write-your-filters-once-run-them-everywhere/ Thu, 26 Mar 2026 00:00:00 +0000 https://blog.rafaelfernandez.dev/posts/criteria4s-1-write-your-filters-once-run-them-everywhere/ Write a predicate once and run it against SQL, MongoDB, Elasticsearch, or any backend. An introduction to criteria4s and its practical take on the Expression Problem. 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.’