[Accepted with modification] SE-0221: Character Properties

Ben_Cohen · August 2, 2018, 4:35pm

SE-0221: Character Properties has been accepted, with the exception of the .isEmoji property.

The core team accepts the principle for the isEmoji property, but wants to continue the discussion of exactly how it should work. Therefore the thread will remain open for this specific topic through August 10th.The other functionality can be merged into master in the meantime.

Ben_Cohen · September 25, 2018, 8:42pm

Updated Review Status

The core team has resolved to change the status of this proposal to accepted with modification, deferring the .isEmoji property to a later proposal.

The core team still believe it is a useful feature for the standard library, but needs more investigation that should not hold up the rest of this proposal.

In addition, the proposal will drop the source-breaking change to the existing FixedWidthInteger.init?. While this would be the preferred naming for a newly proposed initializer, it doesn't clear the bar for a source-breaking change for Swift 5.

kagemiku · June 25, 2019, 8:02am

I have a question about .asciiValue property.
Why type is this UInt8, not Int8? Are there any specific reasons except that ASCII is non-negative value?

github.com

apple/swift/blob/main/stdlib/public/core/CharacterProperties.swift#L51...L55


      
          ///
          /// A character with the value "\r\n" (CR-LF) is normalized to "\n" (LF) and
          /// has an `asciiValue` property equal to 10.
          ///
          ///     let cr = "\r" as Character
          ///     // cr.asciiValue == 13
          ///     let lf = "\n" as Character
          ///     // lf.asciiValue == 10
          ///     let crlf = "\r\n" as Character
          ///     // crlf.asciiValue == 10
          @inlinable
          public var asciiValue: UInt8? {
            if _slowPath(self == "\r\n") { return 0x000A /* LINE FEED (LF) */ }
            if _slowPath(!_isSingleScalar || _firstScalar.value >= 0x80) { return nil }
            return UInt8(_firstScalar.value)
          }
          
          
/// A Boolean value indicating whether this character represents whitespace,
          /// including newlines.
          ///
          /// For example, the following characters all represent whitespace:

xwu · June 25, 2019, 11:33am

Swift uses unsigned types for these purposes throughout the language: ASCII.CodeUnit is a typealias for UInt8.