Re: [sv-bc] 'inside' on real operands

I haven't heard any AMS users bemoaning the lack of "inside" --
lots of models use
   if (A <= thresh)
and maybe a few use
   if (A >= lo_thr && A <= hi_thr)

So, I could see that someone might have a model that had a whole
collection of disjoint allowed ranges, but it's not high on the
list of useful/requested features.

-Geoffrey


Stuart Sutherland wrote:
> Would using reals with the inside operator be useful for Verilog-AMS?  If
> not, I agree with prohibiting reals as operands of inside.  If the
> Verilog-AMS committee sees this as useful, then we should define the
> behavior and any caveats.
> 
> Stu
> ~~~~~~~~~~~~~~~~~~~~~~~~~
> Stuart Sutherland
> Sutherland HDL, Inc.
> stuart@sutherland-hdl.com
> 503-692-0898
>  
> 
>> -----Original Message-----
>> From: owner-sv-bc@server.eda.org 
>> [mailto:owner-sv-bc@server.eda.org] On Behalf Of Jonathan Bromley
>> Sent: Monday, September 10, 2007 7:04 AM
>> To: Geoffrey.Coram; Alsop, Thomas R
>> Cc: Bresticker, Shalom; sv-bc
>> Subject: RE: [sv-bc] 'inside' on real operands
>>
>>> A "user beware" note in the LRM might be appropriate, but I agree
>>> that users should be able to use inside for reals if they want.
>> Whilst this makes sense from a language design point of view,
>> I think it's very dangerous.  The obvious intuitive interpretation
>> of "inside" for reals is "somewhere within this real range". 
>> When combined with the fact that wildcard comparison makes no
>> sense for reals, and the fragility of == on reals, I think the
>> balance should be in favour of prohibiting reals as operands
>> of 'inside' if the right-hand operand is considered to be 
>> a countable set of values.  Furthermore, if we preserve the
>> present meaning of 'inside' whereby its RHS specifies a set
>> of values, then a real range such as [1.0:2.0] makes no sense.
>>
>> I completely agree with Steven Sharp that the following
>> would be both reasonable and (very) useful...
>>
>>   R inside {[1.0:2.0], [3.0:4.5]}
>>
>> and I think that's what users would expect to be able to
>> do - but that makes a specification of a set with an 
>> uncountable number of members; and it suggests that 
>> putting anything *except* such ranges on the RHS of 
>> an 'inside' with real LHS would need to be specified to
>> be erroneous.
>> -- 
>> Jonathan Bromley, Consultant

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