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

I write this before looking at the proposals again:
 
A bit-select can be a variable.
 
In a non-indexed part-select, e.g. name[i:j], both the msb and lsb
indexes need to be elaboration-time constants, otherwise the size
(number of bits), i.e., the type (since size is part of the type) will
vary at run-time.
 
In an indexed part-select, e.g., name[i+:width], the first part of the
index (i.e., starting position) can be variable, the second part of the
index, the width, must be an elab-time constant.
 
Shalom


________________________________

	From: 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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