olegkovalenko

Advanced Functional Programming with Scala - Notes

Copyright © 2017 Fantasyland Institute of Learning. All rights reserved.

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

olegkovalenko

bind s split-window -v -c "#{pane_current_path}"
bind v split-window -h -c "#{pane_current_path}"
bind | split-window -h -c "#{pane_current_path}"
bind - split-window -v -c "#{pane_current_path}"
bind h select-pane -L
bind j select-pane -D
bind k select-pane -U
bind l select-pane -R
bind < resize-pane -L 1
bind > resize-pane -R 1

olegkovalenko

# Based on FUNCTIONAL PEARLS: Monadic Parsing in Haskell
# by Graham Hutton
# University of Nottingham
# Erik Meijer
# University of Utrecht
#
require 'superators' # gem install superators
# parser = ->(x) { [a, l]}
def item
  ->(cs) {

olegkovalenko

*/30 9-17 * * 1-5 say "Stand up and walk around"

olegkovalenko

#   Ruby has #source_location method that returns code location where a method was declared.
# What Ruby lacks is alike functionality that could show where an object was created.
# Below is a very rough solution that may help with tracing object allocations
# by storing the first entry in the caller list during object initialization phase.
# It doesn't work for built-in classes like Fixnum and for classes that don't invoke #initialize()
# like the ones derived from ActiveRecord::Base, but can be potentially tailored to address
# at least the latter case by overriding ActiveRecord::Base.new in addition to overriding #initialize()

class BasicObject
  attr_reader :allocated_at

olegkovalenko

source :rubygems

# We are not loading Active Record, nor Active Resources etc.
# We can do this in any app by simply replacing the rails gem
# by the parts we want to use.
gem "actionpack", "~> 3.2"
gem "railties",   "~> 3.2"
gem "tzinfo"

# Let's use thin

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# Newbie Programmer
def factorial(x)
  if x == 0
    return 1
  else
    return x * factorial(x - 1)
  end
end
puts factorial(6)
puts factorial(0)

olegkovalenko

# RSpec matcher to spec delegations.
#
# Usage:
#
#     describe Post do
#       it { should delegate(:name).to(:author).with_prefix } # post.author_name
#       it { should delegate(:month).to(:created_at) }
#       it { should delegate(:year).to(:created_at) }
#     end