Mastering Typeclass Induction

on YouTube ↗35m

" summary

Shows how to derive typeclass instances for type-level lists by giving a concrete base-case and an inductive implicit that composes head and tail instances, using Scala implicit resolution (no macros). Builds a dynamic dispatch that parses heterogeneous event types into a nested Either-in-Option result using available parsers, paying one static object allocation and one method indirection per list step. Uses the technique in production for SoundCloud event routing and reports no discernable overhead while processing two billion events an hour.

AI-written summary · about

" chapters (12)

1. 0:00Introduction and context
2. 2:04The problem: event parsing
3. 5:05Outline of the talk
4. 5:28Understanding induction
5. 8:25Induction in programming
6. 11:55What are type classes?
7. 14:50Implicit resolution power
8. 16:46Type class induction
9. 20:26Deriving instances
10. 25:25Solving dynamic dispatch
11. 30:56Advanced applications
12. 32:03Q&A and conclusion

" related talks

• 43mMastering Typeclass InductionAaron Levin · Scala World 2017
• 20mType Classes for the Rest of UsAndrew Kuhnhausen · Scale By the Bay 2017
• 33mTYPE CLASSES FROM THE GROUND UPNicolas Rinaudo · Scalar 2020
• 41mThe Dialectics of Type-Level ProgrammingAaron Levin · Lambda World 2016
• 58mSeparating Behavior and Data with Type Classes in ScalaRaúl Raja Martínez · WeCodeFest 2018
• 30mHaving a cake and eating it too Introduction to TypeclassesPawel Szulc · Scalar 2016
• 35mIntroducing Typelevel Scala into an OO environmentMarcus Henry · Typelevel Summit Philadelphia 2016
• 49mOOP versus Type Classes in ScalaAlex Nedelcu · Scala Love in the City 2021