If these are to be added, I'd advocate for renaming `index(of:)` and `index(where:)` to `firstIndex(of:)` and `firstIndex(where:)`, respectively.
On Tue, May 10, 2016 at 13:54 Nate Cook via swift-evolution < [email protected]> wrote: > I've needed these in the past and used them in other languages—any > feedback on this idea? > ------------------------------ > Add last(where:) and lastIndex(where:) Methods to Bidirectional > Collections > > The standard library should include methods for finding the last element > of a bidirectional collection that matches a predicate, along with the > index of that element. > Motivation > > The standard library currently has (or will soon have) methods that > perform a linear search from the beginning of a collection to find an > element that matches a predicate: > > let a = [20, 30, 10, 40, 20, 30, 10, 40, 20] > a.first(where: { $0 > 25 }) // 30 > a.index(of: 10) // 2 > a.index(where: { $0 > 25 }) // 1 > > Unfortunately, there is no such method that searches from the end of a > bidirectional collection. Finding the last of particular kind of element > has multiple applications, particularly with text, such as wrapping a long > string into lines of a maximum length or trimming whitespace from the > beginning and end of a string. > > This limitation can be worked around by using the methods above on the > reversed collection, but the resulting code is truly dreadful. For example, > to find the corresponding last index to a.index(where: { $0 > 25 }), this > unholy incantation is required: > > (a.reversed().index(where: { $0 > 25 })?.base).flatMap({ a.index(before: $0) > }) > > Wat. > Proposed solution > > Bidirectional collections should include three new methods for symmetry > with the existing forward-searching APIs: last(where:), lastIndex(where:), > and lastIndex(of:), specifically for collections of Equatable elements. > > These additions would remove the need for searching in a reversed > collection and allow code like the following: > > a.last(where: { $0 > 25 }) // 40 > a.lastIndex(of: 10) // 6 > a.lastIndex(where: { $0 > 25 }) // 7 > > Much better! > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution >
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