havenwood

def fib n
  a, b = 1, 2
  sum = 0
  while a < n
    sum += a if a.even?
    a, b = b, a + b
  end
  sum
end

havenwood

require 'benchmark'

hash = {}

Benchmark.measure do
  1_000_000.times do
    hash = {}
  end
end.real
#=> 0.245904

havenwood

str = "aaa [first_name] bar [first_name] [last_name]"
last = str.scan(/\[last_name\]/).size
first = str.scan(/\[first_name\]/).size
remaining = str.gsub(/\[(first_name|last_name)\]/, '').size
first * 15 + last * 10 + remaining

havenwood

class MyClass
  attr_accessor :user, :type
  def initialize user: 'smith', type: 'pleb'
    @user = user
    @type = type
  end
end
 
both = MyClass.new user: 'blah', type: 'pleb'
just_one = MyClass.new type: 'pleb'

havenwood

# An octothorp (#) starts a single-line comment.

=begin
   Starting with a =being and ending with a =end
   makes it a multi-line comment.
=end

##
# 1. Variables and flow control.
#

havenwood

# Determines how many cpus the virtual machine should be given. Uses half of
# what's available on the host with a default of 4.
def numvcpus
  begin
    os_cpu_cores / 2
  rescue
    4
  end
end

havenwood

Rails Girls L.A. The Third Level

[ ] I have an editor. It is ___________________.

---

[ ] I can show you where my terminal is and a few commands.

• I can show where I am in the directories.
• List the files in a particular directory.
• Make a directory.

havenwood

require 'fiddle'

class Object
  def cast(as)
    # Make sure iv table of the new class gets initialized.
    as.new.send(:instance_variable_set, :@nil, nil)
    rbasic = Fiddle::Pointer.new(__id__ <<  1)
    as_klass = Fiddle::Pointer.new(as.__id__ << 1)
    
    # Ruby guarantees sizeof(VALUE) == sizeof(void *)

havenwood

# Identity functor that does not give any additional structure
Identity = Struct.new(:value) do
  def fmap(func = nil, &blk)
    f = func || blk;
    Identity.new(f.call(self.value))
  end
end

# Const Functor that preserves its content
Const = Struct.new(:value) do

havenwood

~ ruby json_benchmark.rb
String to JSON
Warming up --------------------------------------
             Oj.dump    24.918k i/100ms
           Yajl.dump     9.461k i/100ms
           JSON.dump    24.797k i/100ms
    MessagePack.dump    44.355k i/100ms
Calculating -------------------------------------
             Oj.dump    267.683k (± 3.4%) i/s -      1.346M in   5.032971s
           Yajl.dump     98.929k (± 2.8%) i/s -    501.433k in   5.072850s