RE: ISAC: Problem with changing IR 2093

Chuck,

I raised the issue of an expression in a case statement being the subject of
a rule relating to locally static subtypes. The issue there is that if the
expression is of a type that is locally static, we know the constraints and
can thus limit the allowable choices to those values of the base type that
satisfy the constraints. For an array type, this amounts to determining the
index range locally statically. A constrained array type allows us to make
that determination.

If we were to allow an unconstrained array type as a locally static subtype,
then we would need to revise the rules for case statements to refer to
expressions of array types for which the index ranges can be determined
locally statically. There are possibly other places where we might need to
make a similar change. Not sure exactly how we'd specify it, of the top of
my head. Any ideas?

Cheers,

PA

--
Dr. Peter J. Ashenden         peter@ashenden.com.au
Ashenden Designs Pty. Ltd.    www.ashenden.com.au
PO Box 640                    VoIP: sip://0871270078@sip.internode.on.net
Stirling, SA 5152             Phone (mobile):  +61 414 70 9106
Australia


> -----Original Message-----
> From: owner-isac@server.eda.org 
> [mailto:owner-isac@server.eda.org] On Behalf Of Chuck Swart
> Sent: Saturday, 6 May 2006 04:52
> To: isac@server.eda.org
> Subject: ISAC: Problem with changing IR 2093
> 
> 
> As you may recall from our last meeting.
> the proposed changes originally included a definition for a 
> locally static unconstrained array type. It was initially 
> decded to remove this 
> definition because
> of problems with static expressions and case statements.
> 
> However, consider the following example:
> 
> constant c1 string := "abc";
> 
> We surely want this to be locally static, but if we are to 
> include type 
> information
> in the definition we need to view the unconstrained array 
> type "string" 
> as locally static.
> 
> Any ideas?
> 
> 
>