class String
  PASSWORD_SETS = {
    /[a-z]/ => 26,
    /[A-Z]/ => 26,
    /[0-9]/ => 10,
    /[^\w]/ => 32
  }
  
  def password_strength
    set_size = 0
    PASSWORD_SETS.each_pair {|k,v| set_size += v if self =~ k}
    
    combinations = set_size ** length
    
    # assuming 1000 tries per second
    days = combinations.to_f / 1000 / 86400
    
    days / 365
  end
end

module Enumerable
  def method_missing(sym, *args)
    if (sym.to_s =~ /^(.+)_with$/) && (msg = args.shift)
      send($1.to_sym) do |x|
        x.send(msg, *args)
      end
    end
  end
end

[1, 2, 3].map_with :to_s

class Fixnum
  def prime?
    ('1' * self) !~ /^1?$|^(11+?)\1+$/
  end
end

pool = ThreadPool.new(10) # up to 10 threads
email_addresses.each do |addr|
  pool.process {send_mail_to addr}
end

require 'thread'

class ThreadPool
  class Worker
    def initialize
      @mutex = Mutex.new
      @thread = Thread.new do
        while true
          sleep 0.001
          block = get_block
          if block
            block.call
            reset_block
          end
        end
      end
    end
    
    def get_block
      @mutex.synchronize {@block}
    end
    
    def set_block(block)
      @mutex.synchronize do
        raise RuntimeError, "Thread already busy." if @block
        @block = block
      end
    end
    
    def reset_block
      @mutex.synchronize {@block = nil}
    end
    
    def busy?
      @mutex.synchronize {!@block.nil?}
    end
  end
  
  attr_accessor :max_size
  attr_reader :workers

  def initialize(max_size = 10)
    @max_size = max_size
    @workers = []
    @mutex = Mutex.new
  end
  
  def size
    @mutex.synchronize {@workers.size}
  end
  
  def busy?
    @mutex.synchronize {@workers.any? {|w| w.busy?}}
  end
  
  def join
    sleep 0.01 while busy?
  end
  
  def process(&block)
    wait_for_worker.set_block(block)
  end
  
  def wait_for_worker
    while true
      worker = find_available_worker
      return worker if worker
      sleep 0.01
    end
  end
  
  def find_available_worker
    @mutex.synchronize {free_worker || create_worker}
  end
  
  def free_worker
    @workers.each {|w| return w unless w.busy?}; nil
  end
  
  def create_worker
    return nil if @workers.size >= @max_size
    worker = Worker.new
    @workers << worker
    worker
  end
end

module Enumerable
  def foldr(o, m = nil)
    reverse.inject(m) {|m, i| m ? i.send(o, m) : i}
  end

  def foldl(o, m = nil)
    inject(m) {|m, i| m ? m.send(o, i) : i}
  end
end

[1, 2, 3, 4, 5].foldl(:+) #=> 15
[1, 2, 3, 4, 5].foldl(:*) #=> 120

[1, 2, 3, 4, 5].foldr(:-, 0) #=> 3
[1, 2, 3, 4, 5].foldl(:-, 0) #=> -15

items = ['abc', 'def', 'ghi']
xml = XML.new do
  instruct!
  reality(:time => Time.now) do
  event do
    type 1
    path "/sharon"
    value "abcdefg"
  end
  list.each {|i| item i}
end
puts xml.to_s

class XML
  # blank slate
  instance_methods.each { |m| undef_method m unless (m =~ /^__|instance_eval$/)}
  
  # Each item in @doc is an array containing three values: type, value, attributes
  
  def initialize(&block)
    @doc = []
    instance_eval(&block)
  end
  
  def method_missing(tag, *args, &block)
    value = block ? nil : args.pop
    attributes = args.pop
    @__to_s = nil # invalidate to_s cache
    if value
      @doc << [:open, tag, attributes] << [:value, value] << [:close, tag]
    else
      @doc << [:open, tag, attributes]
      instance_eval(&block)
      @doc << [:close, tag]
    end
  end
  
  def instruct!(atts = nil)
    @doc << [:instruct, atts || {:version => "1.0", :encoding => "UTF-8"}]
  end

  def to_s
    @__to_s ||= @doc.map{|i| _fmt_part i}.join
  end
  
  alias_method :inspect, :to_s
  
  def _fmt_part(part)
    case part[0]
    when :instruct
      "<?xml #{_fmt_atts(part[1])}?>"
    when :open
      part[2] ? "<#{part[1]} #{_fmt_atts(part[2])}>" :
        "<#{part[1]}>"
    when :close
      "</#{part[1]}>"
    when :value
      part[1].to_s
    end
  end

  def _fmt_atts(atts)
    atts.inject([]) {|m, i| m << "#{i[0]}=#{i[1].to_s.inspect}"}.join(' ')
  end
end

require File.join(LOAD_PATH, 'foobar')

require LOAD_PATH/:foobar

class String
  def /(o)
    File.join(self, o.to_s)
  end
end

class StandardError
  def info
    "#{self.class}: #{message}#$/#{backtrace.join($/)}"
  end
end

class Symbol
  def to_s
    @str_rep || (@str_rep = id2name.freeze)
  end
end

$.first = function(a, b) {return $(a, b).get(0)};