JoelQ

Generic Elm types exercises

A series of exercises to get a feel for how generic types and type variables work in Elm. For each of these, you are given some code that is not compiling. Your task is to get it compiling. You can change the body of the function but not the signature. No cheating with Debug.todo or infinite recursions either 😉

• List
• Maybe
• Html

JoelQ

Elm Types Glossary

There's a lot of type terminology and jargon going around when discussing types in Elm. This glossary attempts to list some of the most common type terms along with synonyms, terms from other language communities, examples, and links to more detailed articles on each topic.

• Custom Type
• Constructor
• Unit Type

JoelQ

#!/bin/sh

set -e

echo "== BUILDING THE APP =="
yarn parcel build src/index.html

echo "== CONFIGURING REDIRECTS  =="
if [ "$CONTEXT" = "production" ]; then
  cp production_redirects dist/_redirects

JoelQ

Redundant if/else - identity

def can_edit?
  if admin?
    true
  else
    false
  end
end

JoelQ

puts "4 line REPL (read eval print loop)"

$stdin.each_line do |line|        # READ
  return_value = eval(line.chomp) # EVAL
  puts return_value               # PRINT
end                               # LOOP

JoelQ

view : Model -> Html Msg
view model =
  div []
    [ div [ class "icon" ] [ span [class "icon-profile" ] [] ]
    , div [ class "icon" ] [ span [ class "icon-clock" ] [] ]
    ]
    
-- REFACTOR TO

view : Model -> Html Msg

JoelQ

class NonEmptyArray
  include Enumerable

  def initialize(first, rest)
    @first = first
    @rest = rest
  end

  def first
    @first

JoelQ

def add(number1, number2)
  number2.times.reduce(number1) { |total| total.next }
end                                                    

add(2,3)
# => 5

def subtract(number1, number2)
  number2.times.reduce(number1) { |total| total.pred }
end

JoelQ

class Hamming
  def self.zip_count(s1, s2)
    s1.chars.
      zip(s2.chars).
      count { |c1, c2| c1 != c2 }
  end

  def self.for_loop(s1, s2)
    distance = 0

JoelQ

class Hamming
  def self.eager(s1, s2)
    s1.chars.
      zip(s2.chars).
      count { |c1, c2| c1 != c2 }
  end

  def self.half_lazy(s1, s2)
    s1.each_char.
      zip(s2.each_char).