Swift-Evolution, I was wondering if there was still some support from the community for adding `clamped(to:)` extensions to `Strideable` and `Comparable` for clamping a value on a provided range.
The proposal is detailed below, sorry if I skipped a step earlier. Also here is a link to the pull request I sent on Github to the Swift-Evolution repository: https://github.com/apple/swift-evolution/pull/641 All the best, - Nick Add clamp(to:) to the stdlib - Proposal: SE-NNNN <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-filename.md> - Authors: Nicholas Maccharoli <https://github.com/Nirma> - Review Manager: TBD - Status: Awaiting review *During the review process, add the following fields as needed:* - Decision Notes: Rationale <https://lists.swift.org/pipermail/swift-evolution/>, Additional Commentary <https://lists.swift.org/pipermail/swift-evolution/> - Bugs: SR-NNNN <https://bugs.swift.org/browse/SR-NNNN>, SR-MMMM <https://bugs.swift.org/browse/SR-MMMM> - Previous Revision: 1 <https://github.com/apple/swift-evolution/blob/...commit-ID.../proposals/NNNN-filename.md> - Previous Proposal: SE-XXXX <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/XXXX-filename.md> <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#introduction> Introduction This proposal aims to add functionality to the standard library for clamping a value to a provided Range. The proposed function would allow the user to specify a range to clamp a value to where if the value fell within the range, the value would be returned as is, if the value being clamped exceeded the upper or lower bound in value the value of the boundary the value exceeded would be returned. Swift-evolution thread: Add a clamp function to Algorithm.swift <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170306/thread.html#33674> <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#motivation> Motivation There have been quite a few times in my professional and personal programming life where I reached for a function to limit a value to a given range and was disappointed it was not part of the standard library. There already exists an extension to CountableRange in the standard library implementing clamped(to:) that will limit the calling range to that of the provided range, so having the same functionality but just for types that conform to the Comparable protocol would be conceptually consistent. Having functionality like clamped(to:) added to Comparable as a protocol extension would benefit users of the Swift language who wish to guarantee that a value is kept within bounds, perhaps one example of this coming in handy would be to limit the result of some calculation between two acceptable numerical limits, say the bounds of a coordinate system. <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#proposed-solution>Proposed solution The proposed solution is to add a clamped(to:) function to the Swift Standard Library as an extension to Comparable and Strideable. The function would return a value within the bounds of the provided range, if the value clamped(to:) is being called on falls within the provided range then the original value would be returned. If the value was less or greater than the bounds of the provided range then the respective lower or upper bound of the range would be returned. It does not make sense to call clamped(to:) with an empty range, therefore calling clamped(to:) and passing an empty range like foo.clamped(to: 0..<0) would result in a fatal error. Given a clamped(to:) function existed it could be called in the following way, yielding the results in the adjacent comments: let foo = 100 // Closed range variant foo.clamped(to: 0...50) // 50foo.clamped(to: 200...300) // 200foo.clamped(to: 0...150) // 100// Half-Open range variant foo.clamped(to: 0..<50) // 49foo.clamped(to: 200..<300) // 200foo.clamped(to: 0..<150) // 100 <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#detailed-design>Detailed design The implementation of clamped(to:) that is being proposed is composed of two protocol extensions; one protocol extension on Comparable and another on Strideable. The implementation for clamped(to:) as an extension to Comparable accepting a range of type ClosedRange<Self>would look like the following: extension Comparable { func clamped(to range: ClosedRange<Self>) -> Self { if self > range.upperBound { return range.upperBound } else if self < range.lowerBound { return range.lowerBound } else { return self } } } The implementation of clamped(to:) as an extension on Strideable would be confined to cases where the stride is of type Integer. The implementation would be as follows: extension Strideable where Stride: Integer { func clamped(to range: Range<Self>) -> Self { guard !range.isEmpty { fatalError("Can not clamp to an empty range.") } return clamped(to: range.lowerBound...(range.upperBound - 1)) } } <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#source-compatibility>Source compatibility This feature is purely additive; it has no effect on source compatibility. <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#effect-on-abi-stability>Effect on ABI stability This feature is purely additive; it has no effect on ABI stability. <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#effect-on-api-resilience>Effect on API resilience The proposed function would become part of the API but purely additive. <https://github.com/Nirma/swift-evolution/blob/2ecfd45f4636e44f1000177fa509b1412cebef92/proposals/NNNN-add-clamp-function.md#alternatives-considered>Alternatives considered Aside from doing nothing, no other alternatives were considered.
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