baweaver

Pattern Matching

Pattern match statements are an extension of the case expression. They introduce a new keyword to case statements: in.

The in expression

in is used in place of when to use pattern matching behaviors. These two syntaxes cannot be mixed.

An in expression is different from when in that it allows one to match against data structures:

baweaver

class Symbol
  def ap(*applied_args)
    -> *block_args {
      if applied_args.empty?
        receiver, *new_args = block_args[0]
        receiver.send(self, *new_args)
      else
        self.to_proc.call(*block_args, *applied_args)
      end
    }

baweaver

Ruby programming
And Gems pushed to GitHub
Cloud based deployments and CI / CD
Tests that will pass on the first try
These are a few of my favorite things

Just Rails new app name
and omakase thinking
convention o'er configuration
and sane default settings

baweaver

class Hash
  alias_method :+, :merge

  def -(other)
    other_keys = Set.new(other.keys)

    # Irrelevant value method
    # reject { |k, _v| other_keys.include?(k) }

    # Relevant value method

baweaver

def double(n) n * 2 end

increment = -> n { n + 1 }

5
|> double    # Method
|> increment # Proc
|> to_s(2)   # self.to_s

baweaver

Tales of the Ruby Grimoire

Introduction

The council of 3.0 had been called, and Scarlet was readying to join them to discuss the future of the land of Ruby. With her was her student, Red, carrying out his latest lesson.

"Now be sure to finish the remaining problems by the time I return, Red. I expect I'll have many fun things to tell you of when I return." said Scarlet.

Red nodded, still writing away on his scrolls, but as Scarlet exited the castle a sly sort of grin grew on his face.

baweaver

class Proc
  def contramap(&fn) self << fn end
end

adds = -> a, b { a + b }.curry

[1, 2, 3].map(&adds[2])
# => [3, 4, 5]

# What if the type on the left doesn't work with `adds`?

baweaver

// Helpers

const MAX_WAIT = 10000;
const POLLING_RATE = 500;

export function timedOut (maxWait) {
  const startTime = Date.now();

  return () => Date.now() - startTime > maxWait;
}

baweaver

TracePoint

What is TracePoint?

A class that provides the functionality of Kernel#set_trace_func in a nice Object-Oriented API.

Well what is set_trace_func?

Establishes proc as the handler for tracing, or disables tracing if the parameter is nil.

baweaver

user_id_tp     = tutor_profiles.index_by(&:user_id)
tutor_subjects = TutorSubject
  .where(tutor_id: user_id_tp.keys)
  .group_by(&:tutor_id)
  .to_h { |uid, subjects| [user_id_tp[uid], subjects.map(&:subject_id)] }

# Faster

user_id_tp     = tutor_profiles.index_by(&:user_id)
hash_of_arrays = Hash.new { |h,k| [] }