RE: [sv-bc] Const cast of Mantis 2398

The indexes in a part select (the select in form [a:b]) must be
constant; otherwise you wouldn't know the width of the selection, which
must be constant. There are other kinds of selects where the indexes do
not have to be constant.

 

--Yulik.

 

From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org] On
Behalf Of Seligman, Erik
Sent: Wednesday, August 13, 2008 5:29 PM
To: Bresticker, Shalom; Brad Pierce; sv-bc@server.eda.org
Cc: sv-sc@eda.org
Subject: RE: [sv-bc] Const cast of Mantis 2398

 

Hold on-- does the index of an expression have to be an elaboration-time
constant?  Wouldn't this invalidate examples in 1900 and 2398, and in
fact defeat the entire concept of assertions & checkers in procedural
code as described in these proposals, since we would not be able to
effectively use procedural variables in indexes?

 

________________________________

From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org] On
Behalf Of Bresticker, Shalom
Sent: Tuesday, August 12, 2008 11:42 PM
To: Brad Pierce; sv-bc@server.eda.org
Subject: RE: [sv-bc] Const cast of Mantis 2398

Yes, that is correct.

 

Shalom

	 

	
________________________________


	From: owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org] On Behalf Of Brad Pierce
	Sent: Wednesday, August 13, 2008 9:34 AM
	To: sv-bc@server.eda.org
	Subject: [sv-bc] Const cast of Mantis 2398

	As I understand the new const'() cast of

	 

	   http://www.eda-stds.org/svdb/view.php?id=2398

	 

	the following part-select would be illegal

	 

	       for (int i = 3; i >= 0; i--) begin

	      y[ const'(i)*2 + 1 : const'(i)*2 ] = i;

	   end

	 

	because const'(i) would be like a simulation-time const
variable, not like an elaboration-time constant expression.

	 

	An expression may be changed to a constant with a const cast.

	 

	             const'(x)

	 

	When casting an expression as a constant, the type of the
expression to be cast shall pass through unchanged. The only effect is
to treat the value as though it had been used to define a const variable
of the type of the expression.

	 

	Correct understanding?

	 

	n  Brad

	
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