pdswan

[14] pry(main)> left.arel.to_sql
=> "SELECT \"users\".* FROM \"users\" WHERE \"users\".\"name\" = $1"
[15] pry(main)> left.to_sql
=> "SELECT \"users\".* FROM \"users\" WHERE \"users\".\"name\" = 'Bill'"
[16] pry(main)>

pdswan

[6] pry(main)> left = User.where(name: "Bill")
  User Load (0.9ms)  SELECT "users".* FROM "users" WHERE "users"."name" = $1  [["name", "Bill"]]
=> []
[7] pry(main)> $ left.union
Error: Couldn't locate a definition for left.union!
[8] pry(main)> left.respond_to?(:union)
=> true
[9] pry(main)> $ left.method_missing

From: /Users/pdswan/code/scratch/rails4_union/rails4/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.0/lib/active_record/relation/delegation.rb @ line 91:

pdswan

[3] pry(main)> ActiveRecordScopeExtensions.union(User.where(name: "Bob"), User.where(name: "Alice")).to_sql
=> "SELECT \"users\".* FROM \"users\" INNER JOIN (( SELECT users.id FROM \"users\"  WHERE \"users\".\"name\" = 'Bob' UNION SELECT users.id FROM \"users\"  WHERE \"users\".\"name\" = 'Alice' )) as users_union_b96cf9af7d77c501088feac76f259ba6 ON users_union_b96cf9af7d77c501088feac76f259ba6.id = users.id"

pdswan

module ActiveRecordScopeExtensions
  def self.union(left, right)
    active_record_klass = left.klass
    
    arel_union = [left, right].map do |scope|
      scope.select("#{active_record_klass.table_name}.id")
    end.reduce(&:union)
    
    temporary_table_name = TemporaryTableName.new([active_record_klass.table_name, "union"].join("_")).to_s
    active_record_klass.joins("INNER JOIN (#{arel_union.to_sql}) as #{temporary_table_name} ON #{temporary_table_name}.id = #{active_record_klass.table_name}.id")

pdswan

waysToChange :: Int -> [Int] -> Int
waysToChange 0 _  = 1
waysToChange _ [] = 0
waysToChange amount denominations@(denomination:xs)
  | amount < 0 = 0
  | otherwise =
    (waysToChange (amount - denomination) denominations) +
    (waysToChange amount xs)

pdswan

" copy all this into a vim buffer, save it, then...
" source the file by typing :so %
" Now the vim buffer acts like a specialized application for mastering vim

" There are two queues, Study and Known.  Depending how confident you feel
" about the item you are currently learning, you can move it down several
" positions, all the way to the end of the Study queue, or to the Known
" queue.

" type ,, (that's comma comma)

pdswan

function Foo(options) {
  var privateInstanceVar = options.thing;
  var publicInstanceVar = options.otherThing;
  
  var publicInterface = {
    publicFunction: publicFunction,
    publicInstanceVar: publicInstanceVar
  };
  
  return publicInterface;

pdswan

class Car
  def initialize(model, engine = ::Engine.new)
    @model = model
    @engine = engine
  end
  
  def running
    engine.running
  end
  

pdswan

source 'https://rubygems.org'

gem 'activerecord', '~> 3.2'
gem 'activerecord-mysql2-adapter'

group :test do
  gem 'rspec'
  gem 'pry'
end

pdswan

var Channels = require('./channels')
  , Emitter = require('events').EventEmitter

var repeater = Channels.createRepeating(250, 'hello', 'world')
  , emitter = new Emitter()
  , emitterTestChannel = Channels.fromEmitter(emitter, 'test')
  , mergedChannel = Channels.merge(repeater, emitterTestChannel)
  , mappedChannel = Channels.map(function() {
                      return Array.prototype.join.call(arguments, ' ')
                    }, repeater)