class Hash

def <(hash)
  hash = Backports.coerce_to_hash(hash)
  return false unless size < hash.size
  each do |k, v|
    v2 = hash.fetch(k) { return false }
    return false unless v2 == v
  end
  true
end

def <=(hash)
  hash = Backports.coerce_to_hash(hash)
  return false unless size <= hash.size
  each do |k, v|
    v2 = hash.fetch(k) { return false }
    return false unless v2 == v
  end
  true
end

def >(hash)
  hash = Backports.coerce_to_hash(hash)
  hash < self
end

def >=(hash)
  hash = Backports.coerce_to_hash(hash)
  hash <= self
end

def any_with_pattern?(pattern = Backports::Undefined, &block)
  return any_without_pattern?(&block) if Backports::Undefined == pattern
  each_entry { |x| return true if pattern === x }
  false
end

def assoc(key)
  val = fetch(key) do
    return find do |k, v|
      [k, v] if k == key
    end
  end
  [key, val]
end

def compact
  h = {}
  each do |key, value|
    h[key] = value unless value == nil
  end
  h
end unless method_defined? :compact

def compact!
  reject! {|_key, value| value == nil}
end unless method_defined? :compact!

def default_proc=(proc)
  if proc == nil # nil accepted in Ruby 2.0
    self.default = nil
    self
  else
    replace(Hash.new(&Backports.coerce_to(proc, Proc, :to_proc)).merge!(self))
  end
end

def default_proc_with_nil=(proc)
  if proc == nil
    self.default = nil
    self
  else
    self.default_proc_without_nil=(proc)
  end
end

def dig(key, *rest)
  val = self[key]
  return val if rest.empty? || val == nil
  raise TypeError, "#{val.class} does not have #dig method" unless val.respond_to? :dig
  val.dig(*rest)
end

def eql?(other)
  other.is_a?(Hash) &&
    size == other.size &&
    all? do |key, value|
      value.eql?(other.fetch(key){return false})
    end
end unless {}.eql?({})

def except(*keys)
  if keys.size > 4 && size > 4 # index if O(m*n) is big
    h = {}
    keys.each { |key| h[key] = true }
    keys = h
  end
  reject { |key, _value| keys.include? key}
end

def fetch_values(*keys, &block)
  keys.map do |k|
    fetch(k, &block)
  end
end

def hash
  h = 0
  each do |key, value|
    h ^= key.hash ^ value.hash
  end
  h
end unless {}.hash == {}.hash

def keep_if
  return to_enum(:keep_if) unless block_given?
  delete_if{|key, value| ! yield key, value}
end

def merge_with_backports(first = {}, *others, &block)
  merge_without_backports(first, &block).
    merge!(*others, &block)
end

def merge_with_backports!(*hashes, &block)
  hashes.each do |h|
    merge_without_backports!(h, &block)
  end
  self
end

def rassoc(value)
  k = key(value)
  v = fetch(k){return nil}
  [k, fetch(k)] if k || v == value
end

def reverse_merge(other_hash)
  other_hash.merge(self)
end unless method_defined? :reverse_merge

def reverse_merge!(other_hash)
  replace(reverse_merge(other_hash))
end unless method_defined? :reverse_merge!

def select!
  return to_enum(:select!) unless block_given?
  raise "can't modify frozen hash" if frozen? # reject! won't do it for empty hashes...
  reject!{|key, value| ! yield key, value}
end

def select_with_hash_return
  return to_enum(:select) unless block_given?
  Hash[select_without_hash_return{|k, v| yield [k, v]}]
end

def shift_with_correct_behaviour_when_empty
  shift_without_correct_behaviour_when_empty unless empty?
end

def slice(*keys)
  h = {}
  keys.each { |k| h[k] = self[k] if key?(k) }
  h
end unless method_defined?(:slice)

def stringify_keys
  Hash[map{|key,value| [key.to_s, value] }]
end unless method_defined? :stringify_keys

def stringify_keys!
  self.replace(self.stringify_keys)
end unless method_defined? :stringify_keys!

def symbolize_keys
  Hash[map{|key,value| [(key.to_sym rescue key) || key, value] }]
end unless method_defined? :symbolize_keys

def symbolize_keys!
  self.replace(self.symbolize_keys)
end unless method_defined? :symbolize_keys!

def to_h
  self.class == Hash ? self : {}.replace(self)
end

def to_h_with_block(&block)
  return to_h_without_block unless block
  map(&block).to_h
end

def to_proc
  h = self
  proc {|*args| h[*args]}
end

def transform_keys
  return to_enum(:transform_keys) { size } unless block_given?
  h = {}
  each do |key, value|
    h[yield key] = value
  end
  h
end unless method_defined? :transform_keys

def transform_keys!
  return enum_for(:transform_keys!) { size } unless block_given?
  self[:trigger_error] = :immediately if frozen?
  h = {}
  begin
    each do |key, value|
      h[yield key] = value
    end
  ensure
    replace(h)
  end
  self
end unless method_defined? :transform_keys!

def transform_keys_with_hash_arg(hash = not_given = true, &block)
  return to_enum(:transform_keys) { size } if not_given && !block
  return transform_keys_without_hash_arg(&block) if not_given
  h = {}
  if block_given?
    each do |key, value|
      h[hash.fetch(key) { yield key }] = value
    end
  else
    each do |key, value|
      h[hash.fetch(key, key)] = value
    end
  end
  h
end

def transform_keys_with_hash_arg!(hash = not_given = true, &block)
  return enum_for(:transform_keys!) { size } if not_given && !block
  return transform_keys_without_hash_arg!(&block) if not_given
  h = {}
  begin
    if block_given?
      each do |key, value|
        h[hash.fetch(key) { yield key }] = value
      end
    else
      each do |key, value|
        h[hash.fetch(key, key)] = value
      end
    end
  ensure
    replace(h)
  end
  self
end

def transform_values
  return to_enum(:transform_values) { size } unless block_given?
  h = {}
  each do |key, value|
    h[key] = yield value
  end
  h
end unless method_defined? :transform_values

def transform_values!
  return to_enum(:transform_values!) { size } unless block_given?
  reject!{} if frozen? # Force error triggerring if frozen, in case of empty array
  each do |key, value|
    self[key] = yield value
  end
end unless method_defined? :transform_values!