RE: [sv-bc] RE: Email Vote: respond by 8AM PDT, Friday, July 30, 2010

Hi, John.

I don't think the LRM says, at least explicitly, when the min-typ-max choice is made.
In practice, in the tools I see, the choice is made at elaboration time, not at run time.
In fact, the choice has to be so, because mintypmax expressions can appear in constant expressions that the elaboration is dependent on.

In any case, the form

parameter P = 1:2:3;

is syntactically and semantically legal and has been so for many years.

What the 2005 LRM said explicitly and got omitted from the 2009 standard was that if the RHS result value is not a real or an integral value (e.g., string, array), then the parameter declaration has to explicitly include the data type of the parameter.

Regards,
Shalom

> -----Original Message-----
> From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of
> John Michael Williams
> Sent: Wednesday, August 04, 2010 4:59 AM
> Cc: sv-bc@eda.org
> Subject: Re: [sv-bc] RE: Email Vote: respond by 8AM PDT, Friday, July
> 30, 2010
>
> Hi Steve.
>
> I agree that a min:typ:max is an expression (of an alternation set
> of numerical values).
>
> The min vs typ vs max choice is taken at runtime and is
> dependent on the simulator. We are talking about
> syntax here (at least, that was my intention).
>
> The compiled and elaborated module will represent a parameter with
> a value of "x:y:x", in which x, y, and z will be numbers. The
> implementation of x:y:z COULD be as you say; or it could be something
> else, such as a string, linked list, or array.
>
> I agree that x:y:z could be a string value, or a subset value, and
> would
> NOT be a numerical value.
>
> Nevertheless, the assignment statement, parameter = x:y:z; should
> be syntactically correct. That was what I meant to be the point
> of my original Email.
>
> On 08/02/2010 07:09 PM, Steven Sharp wrote:
> >
> >> Date: Mon, 02 Aug 2010 10:28:55 -0700
> >> From: John Michael Williams<john@svtii.com>
> >
> >> The new statement makes sense, because a parameter should
> >> be able to store things such as delay triplets:
> >>
> >> parameter MyDelay = 3:4:5;
> >
> > A mintypmax_expression is not a value, nor would a parameter ever
> store it.
> > It is an expression, which evaluates to a single numerical value
> based on
> > which delay is selected during elaboration. The parameter would hold
> the
> > single value that was selected, not the triplet. It is similar to
> writing
> >
> > parameter MyDelay = min_selected ? 3 : (typ_selected ? 4 : 5);
> >
> > The parameter doesn't hold that expression; it holds the result of
> it.

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