Free vs Tagless Final: What, Why, When?
summary
Compares concrete encodings by building a small Scala DSL with integer and string literals, addition, concatenation and string→int conversion, then implements evaluators and a pretty-printer to show what works. Shows initial/ADT, GADT-typed ADT to prevent invalid programs, datatypes à la carte and free monad as initial variants, and tagless final as typeclass combinators; demonstrates adding if, composing extensions, an inlining optimizer (harder in final), round‑trip translations, and recommends initial for inspection-heavy work and final for extensibility and performance.
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chapters (5)
- 0:00Start
- 0:24Free vs Tagless
- 2:08Initial vs Final vs Tagged
- 15:09Case Study: Adding a pretty printer
- 46:08Comparison
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