Hi, I am CC-ing the pharo mailing list because it can be of interest.
I agree with Guillaume that there is a legitimate need for a generic solution. However, at the same time we lose the convenience of simply adding numbers, which is likely to be the most encountered use case. I see a couple of possibilities: - add Collection>>sum: aBlock from: aZeroValue that takes aZeroValue as the default. - add Collection>>sumNumbers: aBlock that takes 0 as default rather than anyOne. What do you think? Cheers, Doru On Mon, Apr 22, 2013 at 10:14 AM, Guillaume Larcheveque < guillaume.larcheve...@gmail.com> wrote: > For example, in Artefact we use Units and I have tried to use sum but it > doesn't works because Units doesn't allow to do 0 + 4 cm which is > inconsistent. > > > 2013/4/22 Alexandre Bergel <alexandre.ber...@me.com> > >> Thanks for letting us know. I cannot see a case where having 0 as the >> initial value does not work as expected. >> >> Cheers, >> Alexandre >> >> >> Le 21 avr. 2013 à 17:35, Tudor Girba <tu...@tudorgirba.com> a écrit : >> >> > Hi, >> > >> > Pharo 2.0 comes with Collection>>sum: >> > >> > Collection>>sum: aBlock >> > "This is implemented using a variant of the normal inject:into: >> pattern. >> > The reason for this is that it is not known whether we're in the >> normal >> > number line, i.e. whether 0 is a good initial value for the sum. >> > Consider a collection of measurement objects, 0 would be the unitless >> > value and would not be appropriate to add with the unit-ed objects." >> > | sum sample | >> > sample := aBlock value: self anyOne. >> > sum := self inject: sample into: [ :previousValue :each | >> previousValue + (aBlock value: each) ]. >> > ^ sum - sample >> > >> > To some extent, this is more generic than the one we had in Moose that >> considered only numbers: >> > Collection>>sum: aSymbolOrBlock >> > ^ self >> > inject: 0 >> > into: [:sum :each | sum + (aSymbolOrBlock value: each)] >> > >> > >> > However, with the Pharo 2.0 implementation the collection must not be >> empty, while the other implementation we get 0. If the collection is empty, >> you get an exception due to anyOne. >> > >> > This induced several errors in metric computations (like number of >> methods of a package when the package had no classes). These are now fixed, >> but I thought I would let you know just in case you want to rely on this >> method. >> > >> > I actually still believe we would benefit from a robust but more >> limited sum:. Perhaps we could have sumNumbers:. >> > >> > Cheers, >> > Doru >> > >> > >> > -- >> > www.tudorgirba.com >> > >> > "If you can't say why something is relevant, >> > it probably isn't." >> > >> > >> > _______________________________________________ >> > Moose-dev mailing list >> > moose-...@iam.unibe.ch >> > https://www.iam.unibe.ch/mailman/listinfo/moose-dev >> >> _______________________________________________ >> Moose-dev mailing list >> moose-...@iam.unibe.ch >> https://www.iam.unibe.ch/mailman/listinfo/moose-dev >> > > > > -- > *Guillaume Larcheveque* > > > _______________________________________________ > Moose-dev mailing list > moose-...@iam.unibe.ch > https://www.iam.unibe.ch/mailman/listinfo/moose-dev > > -- www.tudorgirba.com "Every thing has its own flow"
