On Tue, Sep 27, 2011 at 1:37 PM, Larry White <[email protected]> wrote: > Hi, I had a need to replace the printOn: implementation in ScaledDecimal so > that it didn't include the scale. In other words, I don't want my users to > see '3.02s2'. Being lazy, my first impulse was to remove the code from > printOn: that appends the scale, but I realized I'd have to do that every > time I upgraded my pharo version. > Instead I tried to implement a subclass called DisplayableScaledDecimal and > override printOn. That seems straightforward and smalltalky, but when I do > math on instances of DisplayableScaledDecimal, the results are converted > back to ScaledDecimal. Now I'm looking at re-implementing all the math > logic in scaledDecimal to avoid that. > The problem seems to be in the coerce: method, which reads: > coerce: aNumber > "Note: this quick hack could be replaced by double dispatching" > aNumber class = self class ifTrue: [^self class newFromNumber: aNumber > scale: (scale max: aNumber scale)]. > (aNumber isFraction or: [aNumber isInteger]) ifTrue: [^self class > newFromNumber: aNumber scale: scale]. > ^aNumber > I guess I could override coerce:, but that seems wrong. > So my question to the smalltalk gods on the list is: Could this be fixed > with double dispatching as the comment sort of suggests, and would it be a > useful thing to do?
hm not sure about that. It is usually a good idea that Smalltalk can read object from representation that is outputed from #printOn: , and loosing a scale in #printOn: seems to defeat that rule of the thumb. So maybe avoiding messing with #printOn: is better idea, and introducing a message of your own that converts to the format you wish is a better way. Just my 2c Davorin Rusevljan http://www.cloud208.com/
