Re: ISAC: Problem with changing IR 2093

Peter, and all
I think that I have a simple solution to this.
We do not allow an unconstrained array type as a locally static type,
but we do allow appropriate unconstrained array types in the declaratin of
locally static and globally static constants. I'll update the IR with my 
idea and
we can see if it holds together.

Peter Ashenden wrote:

>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?
>>
>>
>>
>>    
>>
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