[Chandler-dev] Fixed-point number support

[Morgen Sagen]

On Nov 13, 2006, at 3:00 PM, Andi Vajda wrote:

>
> On Mon, 13 Nov 2006, Morgen Sagen wrote:
>
>> I just sent the following email to cosmo-dev...
>>
>>> The issue of supporting floating point numbers in EIM records has  
>>> come up and raised some questions about precision and rounding,  
>>> and whether Chandler needs to get back exactly what it writes to  
>>> Cosmo.  After some IRC discussion in #chandler it seems like it  
>>> makes sense for the places where Chandler needs to share non- 
>>> integer numbers, we should replace those with Decimal (fixed  
>>> point) values.  That would solve the problem of round-trip data  
>>> not coming back to Chandler exactly the same way it was written  
>>> to Cosmo, and also allows CosmoUI to understand these values (in  
>>> other words, they're not just an opaque series of bytes that only  
>>> Chandler understands). Decimal seems to be supported in SQL as well.
>>
>> ...to see if they're on board with supporting the Decimal (fixed- 
>> point number) type, and I also want to get feedback from Chandler  
>> engineers about moving the few shared floating point values (only  
>> one now, but soon two) we have to fixed-point, to avoid the round- 
>> trip precision problems (not getting back exactly what we  
>> published) we face.
>>
>> If we go this route, what would it take to add Decimal support to  
>> the repository (Andi)?
>
> It depends what you want out of it ?
> If python has a decimal type (it looks like it does ?) it should be  
> easy enough to add support for that.
>
> Andi..

Well, if we go this route, I guess it means we want to be able to  
persist values of decimal.Decimal.  Does everyone involved think  
going fixed-point is the right solution?  The decimal module is  
documented here:

http://www.python.org/doc/current/lib/module-decimal.html