VHDL Unknown identifier "signed" in numeric_std

Question

These are my ads. Why doesn't he identify the signed type? I have imported the numeric_std library, and in the documentation I see that it supports signed and unsigned. What is wrong here?

library IEEE; use IEEE.STD_LOGIC_1164.all; use work.my_package.all; entity landmark_1 is generic (data_length :integer := 8; address_length:integer:=3 ); port ( clk:in std_logic; vin:in std_logic; rst:in std_logic; flag: in std_logic; din: in signed(data_length -1 downto 0) done: out std_logic ); end landmark_1; 

Answer 1

try enable use ieee.numeric_std.all;