Re: [sv-ac] P1800 - constant primary as delay in ## : Mantis 1901

Ed,

In the BNF, a degenerate kind of constant_mintypmax_expression is a
constant_expression.

   constant_mintypmax_expression ::=
           constant_expression
         | constant_expression : constant_expression :
constant_expression

So

      constant_primary 
  ::= ( constant_mintypmax_expression ) 
  ::= ( constant_expression )

This tradition can already be found in the earliest versions of the
Verilog BNF.  See, for example,

   http://www.verilog.com/VerilogBNF.html#REF153

   http://www.verilog.com/VerilogBNF.html#REF147


By the way, the constant_* sublanguage in the BNF was only added by
Verilog-2001.  As noted in

   http://www.eda-stds.org/sv-ac/hm/2559.html

I wouldn't have enforced the semantic restrictions of constantness via a
BNF sublanguage, but would have left constant_expression as it was in

   http://www.verilog.com/VerilogBNF.html#REF146

-- Brad

-----Original Message-----
From: Eduard Cerny [mailto:edcerny@synopsys.COM] 
Sent: Wednesday, June 27, 2007 10:37 AM
To: Brad Pierce; sv-ac@eda-stds.org
Subject: RE: [sv-ac] P1800 - constant primary as delay in ## : Mantis
1901

Brad,

yes, for constant_expression this will not do , but then I think it has
to be

cycle_delay_range ::=
	  ## constant_primary
	| ## ( constant_expression )
	| ## [ cycle_delay_const_range_expression ] 

because constant_primary does not allow expression.

constant_mintypmax_expression does not make much sense in the range.
Somehow from the discussion you pointed me to I could not see what
exactly the conclusion was. Should a note be added that this form of
expression is excluded from ## and the repetitions?

Thanks,
ed

> -----Original Message-----
> From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf Of 
> Brad Pierce
> Sent: Wednesday, June 27, 2007 1:05 PM
> To: sv-ac@eda-stds.org
> Subject: Re: [sv-ac] P1800 - constant primary as delay in ##
> : Mantis 1901
> 
> Ed,
> 
> It couldn't be
> 
>     ## constant_expression
> 
> After the ## only a primary could be used, it couldn't for example, be
> 
>     ## P + Q
> 
> without any parens.  For a related example of this problem, see
> 
>    http://www.eda-stds.org/svdb/view.php?id=1480
> 
> I don't understand why a mintypmax expression would be specially 
> disallowed here, since it is already allowed today with an extra pair 
> of parens
> 
>     ## ((e1 : e2 : e3))
> 
> via
> 
>       ## ( constant_expression )
>  ::=  ## ( constant_primary )
>  ::=  ## ( ( constant_mintypmax_expression ) )  ::=  ## ( ( e1 : e2 : 
> e3 ) )
> 
> Requiring the extra pair of parens seems arbitrary to me. See also
> 
>   http://www.boyd.com/1364_btf/report/full_pr/608.html
> 
> which is now Mantis 1054.
> 
> -- Brad
> 
> -----Original Message-----
> From: Eduard Cerny [mailto:edcerny@synopsys.COM]
> Sent: Wednesday, June 27, 2007 9:41 AM
> To: Eduard Cerny; Brad Pierce; sv-ac@eda-stds.org
> Subject: RE: [sv-ac] P1800 - constant primary as delay in ## : Mantis
> 1901
> 
>  
> Brad, however, constant_minTypmax_expression also allows 3 constants 
> which are not allowed in the delay.  Perhaps it might be better to 
> state it as:
> 
> cycle_delay_range ::=
> 	  ## constant_expression
> 	| ## ( constant_expression )
> 	| ## [ cycle_delay_const_range_expression ]
> 
> Would you agree?
> 
> Thanks,
> ed
> 
> 
> > -----Original Message-----
> > From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf Of 
> > Eduard Cerny
> > Sent: Tuesday, June 26, 2007 9:11 PM
> > To: Brad Pierce; sv-ac@eda-stds.org
> > Subject: RE: [sv-ac] P1800 - constant primary as delay in ##
> > : Mantis 1901
> > 
> > In that case yes, it can be easily changed.
> > ed
> >  
> > 
> > > -----Original Message-----
> > > From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On
> Behalf Of
> > > Brad Pierce
> > > Sent: Tuesday, June 26, 2007 5:36 PM
> > > To: sv-ac@eda-stds.org
> > > Subject: RE: [sv-ac] P1800 - constant primary as delay in ##
> > > : Mantis 1901
> > > 
> > > The cycle_delay production that is used in
> procedural_timing_control
> 
> > > and clocking_drive is independent of the cycle_delay_range
> > production used
> > > in sequence_expr.
> > > 
> > > -- Brad
> > > 
> > > -----Original Message-----
> > > From: Eduard Cerny [mailto:edcerny@synopsys.COM]
> > > Sent: Tuesday, June 26, 2007 2:07 PM
> > > To: Brad Pierce; sv-ac@eda-stds.org
> > > Subject: RE: [sv-ac] P1800 - constant primary as delay in
> > ## : Mantis
> > > 1901
> > > 
> > > Brad,
> > > 
> > > I think that ## can also be a cycle delay in procedural
> > code and there
> > > it is not restricted to a constant primary. This is why I did not 
> > > change the syntax but added a constraint. Is that a good
> reason or I
> 
> > > missed something?
> > > 
> > > Thanks,
> > > 
> > > ed
> > >  
> > > 
> > > > -----Original Message-----
> > > > From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On
> > Behalf Of
> > > > Brad Pierce
> > > > Sent: Tuesday, June 26, 2007 4:36 PM
> > > > To: sv-ac@eda-stds.org
> > > > Subject: Re: [sv-ac] P1800 - constant primary as delay in ##
> > > > : Mantis 1901
> > > > 
> > > > Ed,
> > > > 
> > > > Why not just allow any constant_primary after ##?
> > > > 
> > > > Then the rule for cycle_delay_range could be simplified to
> > > > 
> > > >  cycle_delay_range ::=
> > > >        ## constant_primary
> > > >      | ## [ cycle_delay_const_range_expression ]
> > > > 
> > > > plus a footnote that in a cycle_delay_range it shall be
> > > illegal for a
> > > > constant_primary not to evaluate to a nonnegative integer?
> > > > 
> > > > Recall that
> > > > 
> > > >      constant_primary ::= ( constant_mintypmax_expression )
> > > >                       ::= ( constant_expression )
> > > > 
> > > > -- Brad
> > > > 
> > > > -----Original Message-----
> > > > From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On
> > Behalf Of
> > > > Eduard Cerny
> > > > Sent: Tuesday, June 26, 2007 11:31 AM
> > > > To: sv-ac@eda-stds.org
> > > > Subject: [sv-ac] P1800 - constant primary as delay in ## : 
> > > Mantis 1901
> > > > 
> > > > Hi,
> > > > 
> > > > I have created a new mantis entry, 1901, and also attached
> > > a proposal.
> > > > 
> > > > Best regards,
> > > > ed
> > > > 
> > > > --
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