Using functions with many iterations (Package)

[Anissa85]

I want to program a function but it contains many iteration, i do it like this:

LIBRARY ieee ;
USE ieee.numeric_std.all ;
USE ieee.std_logic_1164.all ;
USE ieee.std_logic_arith.all ;
-----------------------------------
package pack_A is
Constant N: integer := 7;
function Substraction ( rin: STD_LOGIC; A: STD_LOGIC_VECTOR (N downto 0); B: STD_LOGIC_VECTOR (N downto 0)) return STD_LOGIC_VECTOR;
end package;
----------------------------------------------
package body pack_A is
function Substraction ( rin: STD_LOGIC; A: STD_LOGIC_VECTOR (N downto 0); B: STD_LOGIC_VECTOR (N downto 0)) return STD_LOGIC_VECTOR is

variable r: STD_LOGIC_VECTOR (N+1 downto 0):=(others => '0');
variable s: STD_LOGIC_VECTOR (N+1 downto 0):=(others => '0');
variable i: integer :=2;
begin
r(0) := rin;
s(0) := a(0) xor b(0) xor r(0);
r(1) := ((not a(0)) and (b(0) or r(0))) or (b(0) and r(0));
if ( i > 0) then
s(i) := a(i) xor b(i) xor r(i);
r(i+1) := ((not a(i)) and (b(i) or r(i))) or (b(i) and r(i));
i := i+1;
if (i=N+1) then
s(N+1) := r(N+1);
end if;
end if;

return s;
end Substraction;

--------------------------------------------------------------
end pack_A;


But it given't any result, however when i did it in process (component) it give result.
Please i need help, THANKS.

 

[TrickyDicky]

whats the problem? functions have to vbe called in processes.

 

[153rd]

The line after begin is also wrong, you're trying to put a 9 bit vector into one bit(r(0).
Furthermore, what is the point of this function?

 

[TrickyDicky]

There are other errors:
You should not mix numeric_std and std_logic_arith in the same file. You should only use numeric_std
There is no loop in the function (that I think you intended to have there) so only bits 0,1 and 2 will get set (once you've fixed the problem 153rd pointed out).