milessabin/shapeless

Add documentation around TypeClass derivation

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#219 opened on Aug 25, 2014

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 (7 comments) (0 reactions) (1 assignee)Scala (3,405 stars) (522 forks)batch import
DocumentationHelp wantedgood first issue

Description

The documentation around typeclass derivation points to a blog post where the derivation process is explained in a very clear manner. The problem is that this blog post mentions that there will be a part 2 that deals with the notion of co-product and how it relates to typeclass derivation. As far as my understanding goes, this blog post never made it out and there is no ressource to find more about the emptycoproduct and coproduct methods that need to need to be implemented in order to derive TypeClassCompanion

Contributor guide

Tech stack
scala
Domain
documentation
Issue type
documentation
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Familiarity with shapeless TypeClass derivationUnderstanding of coproduct in type level programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
The issue asks for documentation on typeclass derivation, specifically the emptycoproduct and coproduct methods. The body notes that a blog post series covers part 1 but part 2 never appeared. To contribute, review the existing documentation at the shapeless site and the source code for TypeClassCompanion. The comments may contain further clarification. Investigate the coproduct related methods in shapeless core and gather examples of their use. Since the issue is old, ensure the information is still relevant for the current version of shapeless.