• Joël Quenneville (Twitter)
• Joël's blog post Elm's Universal Pattern
• map2
• Maybe.map2

MetaphorsSome common metaphors for Elm's Universal Pattern (Applicative Pattern).

• Mapping
• Combining
• Lifting
• Wrapping and unwrapping boxes
• Blog post on Two ways of looking at map functions

Examples* Random generators * Apply mapping functions to vanilla value functions to keep things clean

Tips* Separate branching code from doing code (discussed in-depth in Joël's blog post Problem Solving with Maybe) * Stay at one level of abstraction * Json decoders as combining functions * Scott Wlaschin Railway Oriented Programming * Dillon's blog post Combinators - Inverting Top-Down Transforms * The JSON structure and Elm type don't have to mirror each other - start with your ideal type and work backwards * Applicative pattern * Applicative needs 1) way to construct, 2) map2 or andMap * Json.Decode.Pipeline.required function

Record constructors* Practice writing it with an anonymous function to convince yourself it's equivalent * Record constructors are just a plain old elm function * map2 doesn't take a type, it takes a function - * NoRedInk/elm-json-decode-pipeline is a useful reference for implementing this kind of api on your own * Applicative Laws in Haskell * Monomorphic vs polymorphic * Parser Combinators * elm/parser episode * Joël's blog posts on the ThoughtBot blog * Joël's Random generators talk * Joël's Maybe talk

Some more blog posts by Joël that related to Elm's Universal Pattern:

• Running out of maps
• Pipeline Decoders in Elm

Joël's journey to building a parser combinator:

• Nested cases - https://ellie-app.com/b9nGmZVp9Vca1
• Extracted Result functions - https://ellie-app.com/b9qtqTf8zYda1
• Introducing a Parser alias and map2 - https://ellie-app.com/b9MwZ3y4t8ra1
• Re-implementing with elm/parser - https://ellie-app.com/b9NZhkTGdfya1
• Getting Unstuck with Elm JSON Decoders - because mapping is universal, you can solve equivalent problems with the same pattern (described in this post)