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Removing Elements from a Hash
CodeExpectedActual
h = {}
h[1] = 10
h
 {1=>10} {1=>10} 
h.delete(1)
h
 {} {} 
h = {}
h[5]
 nil nil 
h[5] = 10
h[5]
 10 10 
h[5] = nil
h[5]
 nil nil 
h.keys
 [5] [5] 
h.delete(5)
h.keys
 [] [] 
class Hash
  def delete_value(value)
    delete_if { |k,v| v == value }
  end
end
h = {'apple' => 'green', 'potato' => 'red', 'sun' => 'yellow', 
     'katydid' => 'green' }
h.delete_value('green')
h
 {"sun"=>"yellow", "potato"=>"red"} {"sun"=>"yellow", "potato"=>"red"} 
class Hash
  def remove_hash(other_hash)
    delete_if { |k,v| other_hash[k] == v }
  end
end
squares = { 1 => 1, 2 => 4, 3 => 9 }
doubles = { 1 => 2, 2 => 4, 3 => 6 }
squares.remove_hash(doubles)
squares
 {1=>1, 3=>9} {1=>1, 3=>9} 
h = {}
1.upto(1000) { |x| h[x] = x }
h.keys.size
 1000 1000 
h.clear
h
 {} {}