[Moose-dev] collection>>sum:

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."