# 关键字参数
# required: ruby2.0.x
#
def method(a, b: 1, c: 2)
  puts a
  puts b
  puts c
end

method(0, b: 1, c: 3) # 输出: a=0, b=1, c=3

method(0, b: 1) # 输出: a=0, b=1, c=2

class Base
  def save
    puts "base:save"
  end
end

module Helper
  def save
    puts "helper:save:start"
    super
    puts "helper:save:end"
  end
end

class For < Base
  prepend Helper # use prepend instead of include  def save
    puts "for:save"
  end
end

For.new.save # 输出:  helper:save:start
             #        for:save
             #        helper:save:end

 puts (0..Float::INFINITY).lazy.map {|i|
  ((-1) ** i) / (2*i + 1).to_f
}.take(65536).reduce(:+) * 4
# 输出: 3.141577394800698

• require: 提升 30% 以上的速度
  
• backtrace: lazy的生成栈
  
• GC: 延迟感更低
• stdlib 转移至 rubygems

• https://speakerdeck.com/shyouhei/whats-new-in-ruby-2-dot-0
• http://www.soimort.org/posts/140/