> On May 13, 2016, at 12:12 AM, Patrick Pijnappel via swift-evolution > <swift-evolution@swift.org> wrote: > > For some protocols we'd like to require top-level (free) functions, e.g. for > many math functions such as abs() or sin(). We already do this implicitly for > operators.
Hi Patrick, FYI, we’re very likely to remove this special behavior for operators, by making operator requirements only find operators declared in a conforming type. This would eliminate the special case for operators that exists now, and has other advantages as well. Check out this proposal for more information: https://github.com/apple/swift-evolution/blob/master/proposals/0091-improving-operators-in-protocols.md -Chris > > Proposal > Allow top-level function/property requirements in protocols, e.g.: > > public protocol AbsoluteValuable : SignedNumber { > /// Returns the absolute value of `x`. > @warn_unused_result > toplevel func abs(_ x: Self) -> Self > } > > We'd probably want to require this for operators. This also opens up syntax > if we ever get dynamically dispatched operators. > > public protocol SignedNumber : Comparable, IntegerLiteralConvertible { > /// Returns the result of negating `x`. > @warn_unused_result > toplevel prefix func - (x: Self) -> Self > } > > Currently this is done using the combination of a static method and a > top-level generic function on that protocol. As I understand that approach > does have some benefits in terms of type-checker performance, though I'm not > sure whether that is likely to stay relevant in the future. > > Advantages > Cleaner than current approach (esp. floating point types have tons of > top-level functions) > Makes operators less of a special case > Opens up syntax for member operators > Could also apply to top-level properties (esp. useful if we get generic > properties, for e.g. π<...>) > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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