Blocks, Procs and Lambdas

_questions

1. scope :public_vis, lambda { where(public: false)}
  ...AND 
   scope :public_vis, -> { where(public: false) } do the same thing!  
   is -> the same thing as the lambda key word???

Blocks, Procs and Lambdas

1. Blocks - seen it dozens of times:
  a. Basic
  ``` a = [1,2,3]
      a.map! do |n|
        n**2
      end
      => [1,4,9]
      "Sending the map! method to an array instance with a block of code
  ```
  b.  Yield
  ```
      class Array
      def iterate!
        self.each_with_index do |n, i|
          self[i] = yield(n)
        end
      end
    end
    
    array = [1, 2, 3, 4]
    
    array.iterate! do |n|
      n ** 2
    end
    "The yield here is evaluating the passed in block, and if there are any arguments, they are passed into the block, then the return value is set to the array element w/ given index - cool!"
    
    c. Using &block
      class Array
        def iterate!(&block)
          self.each_with_index do |n, i|
            self[i] = block.call(n)
          end
        end
      end
    
      array = [1, 2, 3, 4]
      
      array.iterate! do |n|
        n ** 2
      end
      "Very similar to yield, except that the iterate method is taking in the block as a param and within the iterator, it's being called w/ the keyword "call" the passed in value(n)"
      
    c.