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@OlivierBlanvillain
OlivierBlanvillain / tfi.md
Last active January 25, 2024 15:59

Revisiting Tagless Final Interpreters

Tageless Final interpreters are an alternative to the traditional Algebraic Data Type (and generalized ADT) based implementation of the interpreter pattern. This document presents the Tageless Final approach with Scala, and shows how Dotty with it's recently added implicits functions makes the approach even more appealing. All examples are direct translations of their Haskell version presented in the Typed Tagless Final Interpreters: Lecture Notes (section 2).

The interpreter pattern has recently received a lot of attention in the Scala community. A lot of efforts have been invested in trying to address the biggest shortcomings of ADT/GADT based solutions: extensibility. One can first look at cats' Inject typeclass for an implementation of [Data Type à la Carte](http://www.cs.ru.nl/~W.Swierstra/Publications/DataTypesA

@nicolasstucki
nicolasstucki / Phantom types implementarion details.md
Last active July 10, 2024 15:07
Update to new scheme

Phantom types

Phantom types are designed to support compile time type evidences without any overhead costs to runtime. Phantom evidences are usually in the form of implicit arguments, which once resolved, can be erased by the compiler.

Because of these properties, phantom types are completely outside of the normal type lattice, and as such these phantom types do not inherit the semantics of Any.