First, is FixedDecimal used in the Money package? �I didn't see is referenced there, so I'm curious where it came from.
There is a definite different between ScaledDecimal and FixedDecimal. �ScaledDecimal �(unless it's been changed recently) keeps the full precision of the original number. �FixedDecimal (and Money, from my short perusal of it), do not - they make sure that the displayed value is exactly what the internal value is. �As an example, check out the following:
x := ((1/3) asScaledDecimal: 2).
x� � � ==> 0.33s2
x = (1/3) ==> true
((33/100) asScaledDecimal: 2) ==> 0.33s2
x = ((33/100) asScaledDecimal: 2) ==> false (!)
x + x ==> 0.67s2 (!)
In general, the last 2 statements are NOT what you want when dealing with Money - if you have an amount, it is a definite amount, and not an approximate amount. �(With the possible exceptions of interim results - but for those, you probably need strict control over exactly how precise the interim results are - which isn't readily available in ScaleDecimal). �This is the main reason I built the FixedDecimal package on SqueakSource. �There, the above statements show:
x := ((1/3) asFixedDecimal: 2).
x� � � ==> 0.33
x = (1/3) ==> true
((33/100)�asFixedDecimal: 2) ==> 0.33
x = ((33/100)�asFixedDecimal: 2) ==> true
x + x ==> 0.66
From my perspecive, ScaledDecimal is great when you want to keep as much precision as possible, but need to SHOW less precision. �It reminds me of science, where you have this measurement that is way more precise than you can really measure, so you 'scale' it back to a precision that is reliable.
-Chris