Bit fields, like in C

Evolution Discussion
13

Here's the FixedWidthIntegers extension:

/// Defines bit-related operations such as setting/getting bits of a number
extension FixedWidthInteger {
  private func mask(_ size: Int) -> Self { (Self(1) << size) - 1 }
  
  /// Returns the bits in the `range` of the current number where
  /// `range.lowerBound` ≥ 0 and the `range.upperBound` < Self.bitWidth
  public func get(range: ClosedRange<Int>) -> Int {
    precondition(range.lowerBound >= 0 && range.upperBound < Self.bitWidth)
    return Int((self >> range.lowerBound) & mask(range.count))
  }
  
  /// Returns the `n`th bit of the current number where
  /// 0 ≤ `n` < Self.bitWidth
  public func get(bit n: Int) -> Int {
    precondition(n >= 0 && n < Self.bitWidth)
    return ((1 << n) & self) == 0 ? 0 : 1
  }
  
  /// Logically inverts the `n`th bit of the current number where
  /// 0 ≤ `n` < Self.bitWidth
  public mutating func toggle(bit n: Int) {
    precondition(n >= 0 && n < Self.bitWidth)
    self ^= 1 << n
  }
  
  /// Sets to `0` the `n`th bit of the current number where
  /// 0 ≤ `n` < Self.bitWidth
  public mutating func clear(bit n: Int) {
    precondition(n >= 0 && n < Self.bitWidth)
    self &= ~(1 << n)
  }
  
  /// Sets to `1` the `n`th bit of the current number where
  /// 0 ≤ `n` < Self.bitWidth
  public mutating func set(bit n: Int) {
    precondition(n >= 0 && n < Self.bitWidth)
    self |= 1 << n
  }
  
  /// Replaces the `n`th bit of the current number with `value` where
  /// 0 ≤ `n` < Self.bitWidth
  public mutating func set(bit n: Int, with value: Int) {
    value.isMultiple(of: 2) ? self.clear(bit: n) : self.set(bit: n)
  }
  
  /// Sets to `0` the bits in the `range` of the current number where
  /// `range.lowerBound` ≥ 0 and the `range.upperBound` < Self.bitWidth
  public mutating func clear(range: ClosedRange<Int>) {
    precondition(range.lowerBound >= 0 && range.upperBound < Int.bitWidth)
    self &= ~(mask(range.count) << range.lowerBound)
  }
  
  /// Replaces the bits in the `range` of the current number where
  /// `range.lowerBound` ≥ 0 and the `range.upperBound` < Self.bitWidth
  public mutating func set(range: ClosedRange<Int>, with value: Int) {
    self.clear(range: range)
    self |= (Self(value) & mask(range.count)) << range.lowerBound
  }
}
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