gEDA: Mime-Version: 1.0

[Stephen Williams <steve-at-NOSPAMicarus_dot_com>]

You're not going to believe this, but:

  reg [3:0] val, y;
  initial begin
    val = 2;
    y = !!val;
  end

As I read the 1995 LRM, this is not legal. Honest! I wonder if the
BNF is FUBAR. Here are the applicable rules:

expression ::= primary
	   | unary_operator primary
	   [etc]

primary ::=
	  number
	| identifier
	| identifier [ expression ]
	| identifier [ constant_expression : constant_expression ]
	| concatenation
	| multiple_concatenations
	| function_call
	| ( mintypmax_expression )

And that's all she wrote. You wrote ``!!val'' which is a ``! primary''
but ``!val'' is not a primary.  !

I would not have guessed that. I wonder if the 2000 LRM is different
in this regard. Anyhow, if you write it like this:

	y = !{!val}

it'll work correctly, as ``{!val}'' *is* a primary. Go figure.

-- 
Steve Williams                "The woods are lovely, dark and deep.
steve@icarus.com              But I have promises to keep,
steve@picturel.com            and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."