I have ScaledDecimal, based on the ANSI Smalltalk standard, but fixed point decimal arithmetic, because that's what the ANSI Smalltalk standard calls for (citing a non-existent part of the LIA standard) but contradicts FixedPoint, a version of that specifically intended for plugging into Squeak and/or Pharo, the snag being that I don't seem to have kept the change set, just the master. I can recreate and donate the change set if anyone would like it. PackedDecimal, which just models VisualAge 31-digit packed decimal for interoperability, but does not do arithmetic. On Tue, 31 Aug 2021 at 19:44, Guillermo Polito <guillermopolito@gmail.com> wrote:
Hi all,
In the past months I worked a bit with it and found many problems too, like: - doing scaled decimal arithmetics losing precision https://github.com/pharo-project/pharo/issues/8668 - strange default scale values https://github.com/pharo-project/pharo/issues/8669
I also got hit with âdowngrading" issues during my vacation coding. For example, when operating a scaled decimal with a float, the result gets downgraded to a float. See
17.777 asScaledDecimal + 0.0
From all the comments I understand that the current implementation is not very useful, they all lead to âdo not use it, instead do XXXâ where XXX is either - write your own - load that other package - use an integer to represent pennies
This this means that either it can be removed, or it can benefit with a new and better implementation. I think it would be interesting to have a better ScaledDecimal implementation, that not only does precise printing but also precise arithmetics.
Or maybe somebody has a good implementation already available?
Cheers, Guille
El 31 ago 2021, a las 0:58, Richard O'Keefe <raoknz@gmail.com> escribió:
Ah, you have run into the insufficiently well known "ScaledDecimal looks like what you need but isn't".
In VisualAge, you have a data type that is basically a reflection of iBM mainframe "packed decimal" format, and perfectly suits the needs of an SQL or COBOL interface. It gives you round-tripping with no error.
In my Smalltalk, ScaledDecimal is a pair (n,s) where n and s are unrestricted integers, representing n * (10 raisedTo: s). This also gives you exact round-tripping and suits the needs of an SQL or COBOL interface.
However, in Squeak and Pharo, ScaledDecimal is something else entirely. Basically, a pair (q,s) where q is an Integer or Fraction, and s is a scale factor used for *printing*. This doesn't just lead to oddities like two unequal ScaledDecimals printing identically, it leads to rounding issues. This is not a bug, it is ScaledDecimal working as designed.
Working within Squeak, the simplest approach is to represent money as pence, and the next simplest is to make or find a Money class.
On Tue, 31 Aug 2021 at 00:02, David Pennington <david@totallyobjects.com> wrote:
Hi everyone. I have a little bank analysis package for my own use but having trouble displaying and storing amounts. I parse out a CSV file from the bank and convert the amounts from text to ScaledDecimal. I then store these into a STON file, which converts them back to text. I then read them in and convert them back to ScaledDecimal again.
I am not used to ~Pharo have spent 24 years using VisualAge Smalltalk so I need a little bit of help because I am getting 1 Penny errors in the conversions. I can cope with this but I would like to get it right.
Can anyone give me a simple means of managing, say, an amount like £76.49 from the bank so that it stops coming back to me as £76.48?
David Totally Objects