class Hash # Returns a hash that represents the difference between two hashes. # # Examples: # # {1 => 2}.diff(1 => 2) # => {} # {1 => 2}.diff(1 => 3) # => {1 => 2} # {}.diff(1 => 2) # => {1 => 2} # {1 => 2, 3 => 4}.diff(1 => 2) # => {3 => 4} def diff(other) dup. delete_if { |k, v| other[k] == v }. merge!(other.dup.delete_if { |k, v| has_key?(k) }) end end