Elm and Ruby

A quick overview of Elm and comparison with Ruby (including how to write better Ruby code).

Transcript

1. Elm Brooke Kuhlmann & Ruby alchemists.io
2. Overview • A functional language that compiles to JavaScript. • A strong focus on simplicity with a concise syntax. 🎉 • No runtime exceptions (no null or unde fi ned)! • Has a friendly, time traveling, debugger! elm-lang.org alchemists.io
3. The Benefits of Elm A brief comparison between Elm and Ruby. elm-lang.org/docs/syntax alchemists.io
4. Elm Lists colors = ["red", "black", "white"] List.head colors -- Result: Just "red" elm-lang.org/docs/syntax#lists colors = [] List.head colors -- Result: Nothing Example 1: Example 2: alchemists.io
5. Ruby Arrays colors = ["red", "black", "white"] colors.first # Result: "red" ruby-doc.org/core-2.6.3/Array.html colors = [] colors.first # Result: nil Example 1: Example 2: alchemists.io
6. Elm Maybe -- The type definition. type Maybe a = Just a | Nothing package.elm-lang.org/packages/elm/core/latest/Maybe ℹ No equivalent in Ruby. alchemists.io
7. Elm Records -- Initial record. planet = {name = "Earth", isHabitable = True} elm-lang.org/docs/syntax#records -- Updated record. updatedPlanet = {planet | isHabitable = False} -- Result: {name = "Earth", isHabitable = False} ℹ All records are immutable by default. alchemists.io
8. Ruby Hashes 💩 # Initial hash. planet = {name: "Earth", habitable: true} ruby-doc.org/core-2.6.3/Hash.html # Mutatation! planet[:name] = "Mars" planet.merge! name: "Mars" # Result {name: "Mars", habitable: true} alchemists.io
9. Ruby Hashes ⭐ # Initial hash. planet = {name: "Earth", habitable: true} ruby-doc.org/core-2.6.3/Hash.html # No mutation. updatedPlanet = planet.merge name: "Mars" # Planet: {name: "Earth", habitable: true} # Updated planet: {name: "Mars", habitable: true} alchemists.io
10. Elm Type Aliases -- MODEL type alias Planet = { name: String, isHabitable: Bool } -- RECORD (function) initialPlanet : Planet initialPlanet = { name = "Planet", isHabitable = True } elm-lang.org/docs/syntax#type-aliases alchemists.io
11. Ruby Contracts gem install contracts github.com/egonSchiele/contracts.ruby Contract String => String => String def label prefix, message "#{prefix}: #{message}" end Requires a gem... ...which then allows for type checking: alchemists.io
12. Elm If Expression elm-lang.org/docs/syntax#conditionals -- Record: planet = {name = "Earth", isHabitable = True} -- Conditional: if planet.isHabitable then "habitable" else "inhabitable" -- Result: "habitable" alchemists.io
13. Ruby If Statement 💩 # Hash: planet = {name: "Earth", habitable: true} # Conditional: if planet[:habitable] "habitable" end # Result: "habitable" www.rubyist.net/~slagell/ruby/control.html ℹ Has potential to answer a nil. alchemists.io
14. Ruby If Statement ⭐ # Hash: planet = {name: "Earth", habitable: true} # Conditional: if planet[:habitable] "habitable" else "inhabitable" end # Result: "habitable" www.rubyist.net/~slagell/ruby/control.html 💡Can be enforced by RuboCop. alchemists.io
15. Elm Custom Types -- Single line. type Status = Terraforming | Habitable | Barren -- Multiple lines. type Status = Terraforming | Habitable | Barren elm-lang.org/docs/syntax#custom-typess ℹ No Ruby equivalent. alchemists.io
16. Elm Case Expression toSentence : Planet -> String toSentence planet = case planet.status of Terraforming -> "Under construction." Habitable -> "Life is good, stop by!" Barren -> "The humans are dead." elm-lang.org/docs/syntax#conditionals ℹ A `_ ->` branch can be used as a catch all (in some situations). planet = {name = "Earth", status = Habitable} alchemists.io
17. Ruby Case Statement 💩 case planet.status when :terraforming "Under construction." when :habitable "Life is good, stop by!" when :barren "The humans are dead." end www.rubyist.net/~slagell/ruby/control.html Planet = Struct.new :name, :status planet = Planet.new "Earth", :habitable alchemists.io
18. Ruby Case Statement ⭐ case planet.status when :terraforming "Under construction." when :habitable "Life is good, stop by!" when :barren "The humans are dead." else fail "Unknown planet status." end www.rubyist.net/~slagell/ruby/control.html 💡Can be enforced by RuboCop. alchemists.io
19. Elm Functions add : Int -> Int -> Int add first second = first + second elm-lang.org/docs/syntax#functions add 2 5 -- Result: 7 alchemists.io
20. Ruby Methods def add first, second first + second end www.rubyist.net/~slagell/ruby/methods.html add 2, 5 -- Result: 7 alchemists.io
21. Ruby Methods (caveats) # Example 1: def add first = 0, second = 0 first + second end www.rubyist.net/~slagell/ruby/methods.html # Example 2: def add first, second return unless first && second first + second end # Example 3: def add first, second Integer(first) + Integer(second) end alchemists.io
22. Summary 🌠 • Immutable by default! • Strong types! • No runtime exceptions! • No nil! www.youtube.com/watch?v=URSWYvyc42M alchemists.io
23. Elm Documentation Getting Started • An Introduction to Elm (online book) • Functional Programming in Elm (online book, partially complete) 💡Read in order listed. Diving Deeper • Elm in Action by Richard Feldman - Book. $40. • Building Web Apps with Elm by The Pragmatic Studio - Screencasts. $50. • Integrating Elm by The Pragmatic Studio - Screencasts. Free. elm-lang.org/docs alchemists.io
24. Thanks 🙇 alchemists.io
25. Let's Connect! alchemists.io @bkuhlmann@mastodon.social