# Re: [vhdl-200x] Proposal for improved physical types

From: Daniel Kho <daniel.kho@tauhop.com>
Date: Fri Jan 09 2015 - 22:46:22 PST
```This is one of the reasons I am supporting the proposal for extended or
arbitrary-length integers:
http://www.eda-twiki.org/cgi-bin/view.cgi/P1076/ArbitraryIntegers

Best regards,
Daniel

On 10 January 2015 at 13:42, Tristan Gingold <tgingold@free.fr> wrote:

> On 10/01/15 06:19, David Koontz wrote:
>
>>
>> On 10/01/2015, at 9:13 am, Tristan Gingold <tgingold@free.fr> wrote:
>>
>>  On 08/01/15 22:41, Kevin Thibedeau wrote:
>>>
>>>>       type frequency is range 0 to physical'high units
>>>>        uHz;
>>>>        milliHz = 1000 uHz;
>>>>        Hz  = 1000 milliHz;
>>>>        kHz = 1000 Hz;
>>>>        MHz = 1000 kHz;
>>>>        GHz = 1000 MHz;
>>>>        THz = 1000 GHz; -- Up to 9.2 THz with a 63-bit positive range
>>>>      end units;
>>>>
>>>
>>> What is wrong with:
>>>
>>>   type frequency is range 0 to 2**63 -1 units
>>>      ...
>>>   end units;
>>>
>>>
>>
>> package physical is
>>      type FREQ is range 0 to 2**63 -1 units  -- line 209
>>          Hz;
>>          kHz = 1000 Hz;
>>          MHz = 1000 kHz;
>>          GHz = 1000 MHz;
>>          THz = 1000 GHz;
>>      end units;
>>
>> ghdl -a top_physicaltest.vhdl
>> top_physicaltest.vhdl:209:30: arithmetic overflow in static expression
>> top_physicaltest.vhdl:209:26: range constraint for a physical type must
>> be static
>>
>> (ghdl-0.31).
>>
>> Analyzes successfully with 2**62 -1, and that sounds like an
>> implementation limit.
>>
>
> Yes, because 2**63 is of type universal integer (a 64 bit type in ghdl),
> but out of the bounds.  Would work if you write the whole number.
>
> (Ada with its arbitrary precision for universal types at compile time only
> doesn't have such issue - and yes, I think this is the best model:
> arbitrary precision at execution time would be a bad idea from a
> performance point of view).
>
> Tristan.
>
>
>
>
>
> --
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>

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```
Received on Fri Jan 9 22:47:06 2015

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