RE: [sv-bc] part selects on arbitrary expressions

Shalom,

Yes, I'd be OK with selects of concatenations as a first step for 2008.
I can imagine someone considering it weird if (a)[0] and a[0] had
different results and not so weird if {a}[0] and a[0] did so.

And it's no less convenient to write {a+b}[0] than (a+b)[0].

BTW would {a+b}[0] return the right-most bit?  If we add support for
selects of concatenations, we should also make sure that the result of
type() applied to a concatenation is clearly defined.

A related nice enhancement would be to allow the concatenation of
unpacked operands (of bit-stream types), returning a simple bit vector.

-- Brad

-----Original Message-----
From: Bresticker, Shalom [mailto:shalom.bresticker@intel.com] 
Sent: Sunday, November 04, 2007 7:20 PM
To: Brad Pierce; sv-bc@eda.org
Subject: RE: [sv-bc] part selects on arbitrary expressions

I have been thinking about this for a long time. I believe that the
simplest thing to do and the way that has the best chance of being
passed within the short time that we have is to define selects on
concatenations. There is no ambiguity in that case. It has some
limitations, you only have vectors, but I believe it would still add a
lot of usefulness.

Shalom 

> -----Original Message-----
> From: owner-sv-bc@server.eda.org
> [mailto:owner-sv-bc@server.eda.org] On Behalf Of Brad Pierce
> Sent: Sunday, November 04, 2007 10:50 PM
> To: sv-bc@server.eda.org
> Subject: Re: [sv-bc] part selects on arbitrary expressions
> 
> Following up to http://www.eda-stds.org/sv-bc/hm/5506.html , I, too, 
> would like to see this enhancement (selects of arbitrary primaries) in

> SV-2008.
>  
> In SV-2005, for any expression 'expr',  one can already declare
>  
>    var type(expr) temp;
>  
> and then write
>  
>    temp = expr;
>    ... temp[5] ...
>  
> But one ought to be able to simply write
>  
>    ... (expr)[5] ...
>  
> More generally, for any primary 'p', one ought to be able to write
>  
>    ... p[5] ...
>  
> Consider the defintion of static cast --
>  
>    "If the expression is assignment compatible with the casting type, 
> then the cast shall return the value that a variable of the casting 
> type would hold after being assigned the expression."
>  
> We could come up with a similar rule that generalizes selects.
>  
> I don't think it's a strong argument against this enhancement to say 
> that the type() operator is not well enough defined, as noted in
> 
>          http://www.eda-stds.org/sv-bc/hm/7082.html
> 
> To me that is just an argument for clarifying the definition of the
> type() operator.
>  
> -- Brad
> 
> --
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