-- This procedure adds two bit_vectors and a carry and returns a sum
-- and a carry.  Both bit_vectors should be of the same length.

procedure Addvec2
	(Add1,Add2: in bit_vector;
	Cin: in bit;
	signal Sum: out bit_vector;
	signal Cout: out bit) is

	variable C: bit := Cin;
	alias n1 : bit_vector(Add1'length-1 downto 0) is Add1;
	alias n2 : bit_vector(Add2'length-1 downto 0) is Add2;
	alias S : bit_vector(Sum'length-1 downto 0) is Sum;

begin
	assert ((n1'length = n2'length) and (n1'length = S'length))
		report "Vector lengths must be equal!"
		severity error;
		
	for i in s'reverse_range loop
		S(i) <= n1(i) xor n2(i) xor C;
		C := (n1(i) and n2(i)) or (n1(i) and C) or (n2(i) and C);
	end loop;
	Cout <= C;
end Addvec2;