Infix operator "+" Error

[wadia]

Hi everybody,

I'm getting the following error:
No feasible entries for infix operator "+"

The program is as follow:
-- Fichier : Compteur_bcd10.vhdl
-- Description : Compteur BCD de 0 à 9
library IEEE;
use IEEE.std_logic_1164.all;
-- use IEEE.numeric_std.all;

entity compteur_bcd10 is -- définition des entrées/sorties
port(clk, en, rst_n : in std_logic;
rco : out std_logic;
q : out std_logic_vector(3 downto 0));
end compteur_bcd10;

architecture behav of compteur_bcd10 is
signal cnt : std_logic_vector(3 downto 0); --std_logic_vector(3 downto 0); -- signal interne
begin
q <= cnt; -- q, la sortie vaut la valeur du compte actuel en tout temps
process(clk, rst_n) -- process sensible à l'horloge et au "clear"
begin
if (rst_n='0') then -- "clear" asynchrone
cnt <= (others => '0');
rco <= '0';
elsif (clk'event and clk='1') then -- au front montant
if (en='1') then -- si enable vaut 1
if (cnt = "1010") then -- si on atteint 9, on fait un rco
cnt <= (others => '0'); -- et on remet le compteur a 0
rco <= '1';
else -- sinon, on compte
"ERROR LINE" cnt <= cnt + "0001";
rco <= '0';
end if;
else
cnt <= cnt;
rco <= '0';
end if;
end if;
end process;
end behav;

Could you please help me with this?

Thanks & Regards,

Walter

Note: I've tried using unsigned, but the error is still there.

 

[wadia]

Solution to No feasible entries for infix operator "+"

I've found the solution to this problem by adding the following line to my program:

use IEEE.std_logic_unsigned.all;

That's it !

Thanks anyway.