Unary Ampersand Example: Proc to Block

proc_to_block.rb

items = {
  'a' => 'aardvark',
  'b' => 'banana',
  'c' => 'cookies',
  'd' => 'dog'
}

criteria = Proc.new { |key, value| value == 'banana' }
items.select(&criteria) # => {"b"=>"banana"}
items.reject(&criteria) # => {"a"=>"aardvark", "c"=>"cookies", "d"=>"dog"}