JoelQ

class Tally
  def self.empty
    new({})
  end

  def initialize(raw)
    @raw = empty_hash.merge raw.slice(:small, :medium, :large)
  end

  # Accessors

JoelQ

How not to implement a multi-step form

"That ticket touches the wizard code? Why don't YOU take that one". The wizard in question is so gnarly my colleagues are afraid to touch it.

Looking at the code through the lens of conditional cardinality reveals what went wrong and how we can make things better. This mental model will change the way you think about structuring logic and help you take your conditional code from scary to delightful.

Description

This talk is aimed at an intermediate to advanced audience. While it will driven by a practical example (refactoring a multi-step form), it will mainly be about some more theoretical principles and mental models for structuring conditional code.

JoelQ

The Math Every Programmer Needs

Abstract

Leave your fear of math behind along with the equations and symbols, we're headed to Ruby-land! On this whirlwind tour, we’ll explore how to write better conditionals with Boolean algebra, figure out how many test cases we need with combinatorics, a mental model for breaking down large tasks with graph theory, and more.

You’ll leave this talk equipped to better do your job with some ideas, techniques, and mental models from the wonderfully practical world of discrete math.

Details

JoelQ

class Tree
  attr_reader :val, :left, :right

  def self.empty
    EmptyTree.new
  end

  def self.leaf(val)
    new(val, empty, empty)
  end

JoelQ

class Dollar
  attr_reader :cents

  def initialize(cents:)
    @cents = cents
  end

  def hash
    [self.class, cents].hash
  end

JoelQ

require "date"

class Month
  include Comparable

  MONTHS_PER_YEAR = 12

  def self.from_date(date)
    self.from_parts(date.year, date.month)
  end

JoelQ

class Tree
  attr_reader :value, :left, :right

  def initialize(value, left, right)
    @value = value
    @left = left
    @right = right
  end

  def reduce(initial, &block)

JoelQ

class Add
  def self.mempty
    new(0)
  end

  def initialize(number)
    @number = number
  end

  attr_reader :number

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