##
# Struct
#
# ISO 15.2.18

if Object.const_defined?(:Struct)
  class Struct

    ##
    # Calls the given block for each element of +self+
    # and pass the respective element.
    #
    # ISO 15.2.18.4.4
    def each(&block)
      self.class.members.each{|field|
        block.call(self[field])
      }
      self
    end

    ##
    # Calls the given block for each element of +self+
    # and pass the name and value of the respectiev
    # element.
    #
    # ISO 15.2.18.4.5
    def each_pair(&block)
      self.class.members.each{|field|
        block.call(field.to_sym, self[field])
      }
      self
    end

    ##
    # Calls the given block for each element of +self+
    # and returns an array with all elements of which
    # block is not false.
    #
    # ISO 15.2.18.4.7
    def select(&block)
      ary = []
      self.class.members.each{|field|
        val = self[field]
        ary.push(val) if block.call(val)
      }
      ary
    end

    def _inspect
      name = self.class.to_s
      if name[0] == "#"
        str = "#<struct "
      else
        str = "#<struct #{name} "
      end
      buf = []
      self.each_pair do |k,v|
        buf.push [k.to_s + "=" + v._inspect]
      end
      str + buf.join(", ") + ">"
    end

    ##
    # call-seq:
    #   struct.to_s      -> string
    #   struct.inspect   -> string
    #
    # Describe the contents of this struct in a string.
    #
    # 15.2.18.4.10(x)
    #
    def inspect
      begin
        self._inspect
      rescue SystemStackError
        "#<struct #{self.class.to_s}:...>"
      end
    end

    ##
    # 15.2.18.4.11(x)
    #
    alias to_s inspect
  end

  ##
  # call-seq:
  #   hsh.dig(key,...)                 -> object
  #
  # Extracts the nested value specified by the sequence of <i>key</i>
  # objects by calling +dig+ at each step, returning +nil+ if any
  # intermediate step is +nil+.
  #
  def dig(idx,*args)
    n = self[idx]
    if args.size > 0
      n&.dig(*args)
    else
      n
    end
  end
end