RE: [sv-bc] DataTypes: BNF changes

> The datatypes groups voted to disallow <nettype> followed by 'reg' as a
> lexical restriction.

I cannot find this restriction anyplace in the proposed BNF, chapter 4 or 5
changes to the LRM.

Is it an oversight that this was left out?

How exactly was this restriction formulated?

> -----Original Message-----
> From: Rich, Dave [mailto:Dave_Rich@mentorg.com]
> Sent: Wednesday, November 10, 2004 2:32 PM
> To: Mark Hartoog; Steven Sharp; btf-dtype@boyd.com; sv-bc@eda.org
> Subject: RE: [sv-bc] DataTypes: BNF changes
>
>
> Mark,
>
> The datatypes groups voted to disallow <nettype> followed by 'reg' as a
> lexical restriction.
>
> This would still allow
>
> typedef reg T;
>
> tri T w;
>
>
> But I was in favour of
>
> tri <T> w;
>
> for other reasons you mentioned.
>
> Dave
>
>
>
> -----Original Message-----
> From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Mark
> Hartoog
> Sent: Wednesday, November 10, 2004 2:21 PM
> To: Steven Sharp; btf-dtype@boyd.com; sv-bc@eda.org
> Subject: RE: [sv-bc] DataTypes: BNF changes
>
> There are some unfortunate corner cases in the syntax for data types
> on wires.
>
> tri reg w1; // declares a net with tri resolution and reg data type.
> trireg w2; // declares a net with trireg resolution and default (logic)
> // data type.
> trireg reg w3; // declares a net with trireg resolution and reg data
> type.
>
> I'm not sure there is anything that can be done about this. I notice at
> one time some of the emails were using a template like syntax:
>
> tri<reg> w1;
> trireg w2;
> trireg<reg> w3;
>
> which is syntactically clearer on this point, but I think has other
> problems.
> Declarations like:
>
> tri signed [7:0] w1;
>
> are legal v2k, but "signed [7:0]" is now the data type specifier with
> default logic data type. We can not force <> here for backwards
> compatibility, so it would be funny if
>
> tri <logic signed [7:0]> w1;
>
> putting in the default data type now required <>.
>
> Another alternative would be to outlaw 'reg' data type on wires
> and only allow logic. I don't really like that either.
>
> Since wire types tri and trireg are not commonly used, I don't expect
> this to be a very serious practical problem, and I guess I would rather
> live with this problem then any of the solutions I can think of.
>
> Mark Hartoog
> 700 E. Middlefield Road
> Mountain View, CA 94043
> 650 584-5404
> markh@synopsys.com
>
>
>
>
Received on Wed Nov 10 14:42:52 2004