VHDL question

[Altera_Forum]

Hi all! 

 According to std.standard:  TYPE string IS ARRAY ( positive RANGE <> OF character);  "hello" is a valid string litteral "" is a valid string litteral too, it is the empty string.   Let  TYPE foo IS ARRAY ( positive RANGE <> OF integer);  (0, 1, 1, 2, 3, 5) is a valid foo litteral  What is the litteral for an empty foo?  Thx  Julien

[Altera_Forum]

Did you try () or (null)?

[Altera_Forum]

The only way I know is to create a null array constant, and use that in place of a literal: 

 constant NULL_FOO : foo(1 downto 2) := (others => 0);

[Altera_Forum]

yes. 

 neither of these work :(

[Altera_Forum]

OK for 1 downto 2 range. 

 Any other (cleaner) way?

[Altera_Forum]

I dont think there is. Could you explain why you want to do it? 

 another less "clean" way - declare a pointer to foo.  type foo_ptr_t is access foo;  variable foo_ptr : foo_ptr_t;  and then you can actually compare it to null:  if foo_ptr = null then  ...etc  But that is getting rather extreme.