I vote for “mapNonNil”, “mapDroppingNil” or “unwrappingMap”(or some variations using unwrap).
It’s not pretty, but does the job! Em qua, 15 de nov de 2017 às 22:36, Greg Parker via swift-evolution < [email protected]> escreveu: > On Nov 15, 2017, at 2:31 PM, BJ Homer via swift-evolution < > [email protected]> wrote: > > On Nov 15, 2017, at 3:05 PM, Tino Heth via swift-evolution < > [email protected]> wrote: > > Odd… exactly that is the reason why I think filterMap is the worst choice: > > > Both are established terms of art, but one has a meaning that doesn’t fit > to the operation. > Applying filter can remove elements, but it can never change types (I feel > kind of silly to repeat this over and over, but so far, nobody took the > time to falsify this). > > > The concern about filter changing types is only relevant if you think of > the filter applying to the *result* of the map, instead of being a part > of the filterMap operation itself (an operation that is distinct from map > ). > > Let’s imagine that we had this instead: > > enum SelectiveMapResult<T> { > case use(T) > case ignore > } > > extension Sequence { > func selectiveMap<T>(_ selectiveTransform: (Element)-> > SelectiveMapResult<T>) -> [T] > } > > let actualNumbers = > ["1", "2", "apple", "banana", "5"].selectiveMap({ (x)-> > SelectiveMapResult<Int> in > if let value = Int(x) { return .use(value) } > else { return .ignore } > }) > > actualNumbers == [1, 2, 5] > > > The “selective” part of this operation doesn’t feel like it’s changing the > type of the result, because SelectiveMapResult is easily understood to > not be part of the mapping transformation; it just exists to tell us > whether we should *use the result* of that particular transformation. > Likewise, I don’t feel like the optional in filterMap is part of the > mapping operation; it’s just serving the same role as SelectiveMapResult. > (It should be obvious that SelectiveMapResult is just Optional with > another name here.) > > > "selectiveMap" feels better in part due to grammar. "map" is obviously the > verb and "selective" is obviously a modification of "map". "selectiveMap" > is therefore performing some sort of special map operation. > > "filterMap" feels bad for the same reason that "selectMap" would feel > worse than "selectiveMap". "filter" and "map" are both verbs in this > context. Grammatically the analogue to "selectiveMap" would be > "filteredMap" or "filteringMap". > > But even then "filteredMap" or "filteringMap" is insufficient to describe > the operation. You additionally need to know that the "filter" here is not > ordinary "filter", but instead the special case "filter { $0 != nil }". > > > The name filterMap focuses on removing the ignored values, as does > compactMap. The name selectiveMap focuses on retaining the non-ignored > values. I’m not sure whether focusing on the positive or negative aspects > is clearer here. I don’t particularly like the name compactMap, simply > because I don’t have a lot of experience with languages that use “compact” > to mean “drop the nil values”, and without that experience it doesn’t seem > intuitive. I think filterMap is better. But if we introduced > Sequence.compact() alongside .compactMap(), I’d probably get used to it. > > > Swift doesn't use "filter" to mean "drop the nil values" either. > > > "compactMap" is okay if "compact" is added. Is "compact" a common enough > operation in practice to pull its own weight? > > "mapSome" is great if you know about Optional.Some but terrible if you > don't. ("Okay, it maps some elements, but which ones?") > > "mapNonNil" is obvious and ugly and perhaps its obviousness makes it a > winner. > > > -- > Greg Parker [email protected] Runtime Wrangler > > > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution >
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