Writing unit tests have found that there’s no such thing like Int.random(), only things like Int.random(in:). Findings after small research:

  • Instead of Int.random(in: Int.min ... Int.max) one could write Int.random(in: .min ... .max).
  • Exclusion of random() was deliberate decision to protect users from a common error called modulo bias.
  • There’s one random(), Bool.random().
  • Before Swift 4.2 people were using GameplayKit to shuffle arrays. GameKit has shaped random number generators, like GKGaussianDistribution or GKShuffledDistribution.
  • There’s a bunch of initializers of numeric types, like Int8(exactly: 1_000), Int8(clamping: 500), Int8(truncatingIfNeeded: q).
  • That is smart use of generic public static func >> <RHS>(lhs: Self, rhs: RHS) -> Self where RHS : BinaryInteger.
  • Quotient /ˈkwoʊʃənt/ is a term of a result of division, “Частка” in Ukrainian, “Частное”” in Russian.
  • signum() returns -1, 0 or 1.
  • quotientAndRemainder(dividingBy: n) returns tuple (quotient, remainder).
  • interesting example inside of FixedWidthInteger:
    extension FixedWidthInteger {
      var binaryString: String {
          var result: [String] = []
          for i in 0..<(Self.bitWidth / 8) {
              let byte = UInt8(truncatingIfNeeded: self >> (i * 8))
              let byteString = String(byte, radix: 2)
              let padding = String(repeating: "0",
                                       count: 8 - byteString.count)
              result.append(padding + byteString)
          return "0b" + result.reversed().joined(separator: "_")
  • and here goes my first PR into Swift fixing follow up comment for above mentioned snippet for binaryString.
  • FixedWidthInteger has set of operations like addingReportingOverflow(n) returning tuple (partialValue: Self, overflow: Bool). And multipliedFullWidth(n) returning tuple (high: Self, low: Self.Magnitude) as well as a little bit trickier dividingFullWidth. Don’t understand these two. But hope I will recall this when I need to deal with overflows in miltiplication and/or division.
  • leadingZeroBitCount and nonzeroBitCount might be useful. As well as bigEndian, littleEndian, byteSwapped.
  • Interesting to remember about existence of initializers like Int("-123", radix: 8) where radix could be from range 2...36. Why not up to 64? TODO: look into implementation. Important to remember that string parameter should be trimmed otherwise it fails!
  • Operations like masking addition assignment operator &+= exist. Swift programming language book refers these as Overflow Operators while documentation - Advanced Operators.
  • words property exists in integer types. It’s collection of words representing integer type.

May be once I will have time to browse all 40K lines of Integer in Swift.