class GBN_KEYED_PAIR [G->COMPARABLE, H]
  -- Ordered pair consisting of key and data.
  -- The key cannot be changed after creation,
  -- but key and item can be read and item
  -- changed at any time.

inherit
  COMPARABLE
  redefine
    is_equal, out
  end

	-- necessary to redefine is_equal because
	-- of ensure condition involving trichotomy.

creation
  make

feature

is_equal ( other : like Current ) : BOOLEAN is
  do
    Result := key . is_equal ( other . key )
  end

infix "<" (other: like Current): BOOLEAN is
  do
    Result := (key < other . key)
  end

key : G
item : H

make ( k: G ) is
  do
    key := k
  end

put ( titem:  H ) is
  do
    item := titem
  end

out : STRING is
    do
	-- changed to_string to out, because
	-- to_string not recognised in STRING!
      !! Result . copy ( "( " )
      Result . append ( key . out )
      Result . append ( ", " )
      Result . append ( item . out )
      Result . append ( " )" )
    end

end -- class GBN_KEYED_PAIR