RE: [vhdl-200x-dta] FW: [vhdl-200x] Revised white paper on type genericity

Steve,

Signal assignment is problematic, since you don't know just from the formal
type whether the actual type might be illegal for signals. It might, for
example, be (or include an element of) an access type.

We encountered the same issue relating to private types in SUAVE, and dealt
with it by indicating in a private type declaration whether the type might
include an access type. In the v2 genericity proposal, since we removed the
contract information from the formal type definition, we consequently lost
the ability to safely use a formal type for a signal.

At this stage, I don't think the loss is a problem. Since there is no
contract information, about the only thing you can do with type generics is
use them for defining generic containers. If you needed to communicate the
content of a container between processes in a test bench, you could use
shared variables to encapsulate the containers.

I look forward to hearing Bhasker's response.

Cheers,

PA

--
Dr. Peter J. Ashenden                        peter@ashenden.com.au
Ashenden Designs Pty. Ltd.                   www.ashenden.com.au
PO Box 640                                   Ph:  +61 8 8339 7532
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Australia                                    Mobile: +61 414 70 9106
> -----Original Message-----
> From: owner-vhdl-200x-dta@eda.org 
> [mailto:owner-vhdl-200x-dta@eda.org] On Behalf Of Peter Ashenden
> Sent: Wednesday, 21 April 2004 18:05
> To: vhdl-200x-dta@eda.org
> Subject: [vhdl-200x-dta] FW: [vhdl-200x] Revised white paper 
> on type genericity
> 
> 
> From: owner-vhdl-200x@eda.org 
> [mailto:owner-vhdl-200x@eda.org] On Behalf Of Bailey, Stephen
> Sent: Wednesday, 21 April 2004 16:00
> To: 'Jonathan Bromley'; vhdl-200x@eda.org
> Subject: RE: [vhdl-200x] Revised white paper on type genericity
> 
> 
> All,
> 
> I'm also concerned that signal assignment is not one of the 
> operators included.  Except for access and protected types, 
> there should be no problem with signal assignment.  But, 
> maybe it isn't needed.
> 
> Bhasker, since this proposal is intended to address the 
> immediate needs in the testbench and verification area 
> (container objects proposals), can you comment on whether 
> signal assignment would be needed?
> 
> -Steve Bailey
> 
> 
> > ... sounds like very good stuff, but I don't understand the need for
> > this restriction (section 6 Formal Generic Types, first paragraph):
> > 
> >    An interface type declaration defines a formal generic 
> >    type that can denote any type. The generic unit can only
> >    assume that operations available for all types are 
> >    applicable, namely, variable assignment, equality and 
> >    inequality operations.
> > 
> > Presumably an object of the generic type can be passed as
> > an actual parameter to a subprogram?  In which case, why
> > not allow it to appear as an operand in an infix
> > expression?
> > --
> > Jonathan Bromley, Consultant
> > 
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