VHDL question

Question

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 · Answer

Did you try () or (null)?

altera_forum · Answer

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 =&gt; 0);

altera_forum · Answer

yes.  neither of these work :(

altera_forum · Answer

OK for 1 downto 2 range.  Any other (cleaner) way?

altera_forum · Answer

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.

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