Joël Quenneville 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 😉

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

Redundant if/else - identity

def can_edit?
  if admin?
    true
  else
    false
  end
end

	class Add
	def self.mempty
	new(0)
	end

	def initialize(number)
	@number = number
	end

	attr_reader :number

	#!/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

	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

	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

	class NonEmptyArray
	include Enumerable

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

	def first
	@first

	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

	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