用each实现map方法

my_map.rb

# one dimensional array
# yield
class Array
  def my_map
    arr = []
    each {|n,i| arr << yield(n)}
    arr
  end
end

# call
class Array
  def my_map &block
    arr = []
    each {|i| arr << block.call(i)}
    arr
  end
end

# multidimensional array
# yield
class Array
  def my_map
    self.each_with_index do |n,i|
      self[i] = yield(n)
    end
  end
end

# call
class Array
  def my_map &block
    self.each_with_index do |n,i|
      self[i] = block.call(n)
    end
  end
end