type conversion of a custom enumeration type

Hi,

I defined an enumeration type ("reg") in a package header:

1

LIBRARY ieee;

2

USE ieee.std_logic_1164.all;

3

USE ieee.std_logic_arith.all;

4

...

...

1

type reg is (R0, R1, R2, R3);

...and a conversion function which converts type "std_logic_vector" to 
my type "reg":

1

function CONVTOREG (DATA :std_logic_vector) return reg;

In the body of the package I have the corresponding implementation of 
this conversion function:

1

  function CONVTOREG (DATA :std_logic_vector) return reg IS

2

    variable result :integer; 

3

      begin 

4

       result := CONV_INTEGER(unsigned(DATA));

5

      return reg'VAL(result);

6

  end function;

This works fine. Now I need another conversion function which converts 
the type "reg" back to std_logic_vector" which is declared like this:

1

function CONV_REG_TO_STDLV (DATA :reg) return std_logic_vector;

But I don't know how to implement that since there is no type conversion 
which accepts my enumeration type. Has anybody an idea how to do that?

Thanks a lot!

Best regards.

M.R.