modeling-users

[Modeling-users] Money and Modeling

[Yannick G. <yan...@sa...>]

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What are you guys doing with monetary values ?

mx.DateTime is a really nice class for dates management. Is there a class o=
ut=20
there for money ?

I'm not certain I fully understand how Modeling treats the SQL decimal
type.  Decimal should be fixed points but retrieving and attribute
defined by :
   <attribute displayLabel=3D''
              scale=3D'4'
              name=3D'currencyRate'
              isRequired=3D'1'
              externalType=3D'numeric'
              defaultValue=3D'None'
              isClassProperty=3D'1'=20
              precision=3D'10'=20
              columnName=3D'currency_rate'
              type=3D'string'
              width=3D'0'/>

gives a float which is not quite fixed point...  Is there anything wrong wi=
th=20
my model ?

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Yannick Gingras
Byte Gardener, Savoir-faire Linux inc.
(514) 276-5468

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Re: [Modeling-users] Money and Modeling

[Yannick G. <ygi...@yg...>]

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On Tuesday 08 July 2003 17:19, you wrote:
> Fixed point doesn't exist in the default python so . You always retrieve
> a numeric but it's map to
> a float in python.  And please be carefull about this as, python do some
> strange round while
> using print() and stuff like that . I got a quick explain here in my
> bookmark but it's in french .
>
>  >>> 6+1
> 7 this is a integer
>  >>> 6.0 + 1
> 7.0  this is a float
>
>  >>> print "%s" % ( 6.0 + 1)
> 7.0
>  >>> print "%d" % ( 6.0 + 1)
> 7

Argh !

  >>> val = 1.1
  >>> val
  1.1000000000000001

I just created a small amount of money from nowhere.  A really small one but 
imprecision of floats adds up and financial controllers really hate when some 
money appears from nowhere...

  >>> 45.678
  45.677999999999997

I just lost a small amount of money in the deep void.  A really small
one but...

How about : 

  class FixedPoint:
     def __init__(self):
        self._val = 0 # int
        self._pointPos = 0 # int too

With a few operators overloaded it would map nicely with the SQL decimal and 
could easily serialize to a simple tuple (like mx.DateTime.tuple())

If it make sense I can send a sketchy class that could be shipped with
Modeling.

- -- 
Yannick Gingras
Coder for OBB : Omniscient Behaviouristic Baroque
http://OpenBeatBox.org
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