sliced-where.swift

extension Collection {
  func sliced(
    where predicate: (Element, Element) -> Bool
  ) -> [SubSequence] {
    var result: [SubSequence] = []
    var start = startIndex
    
    for (i, j) in zip(indices, indices.dropFirst()) {
      if predicate(self[i], self[j]) {
        result.append(self[start..<j])
        start = j
      }
    }
    
    result.append(self[start...])
    return result
  }
}

[1, 1, 2, 2, 2, 3, 4, 4].sliced(where: !=)
// [[1, 1], [2, 2, 2], [3], [4, 4]]
[1, 1, 1, 1, 1, 1, 1].sliced(where: !=)
// [[1, 1, 1, 1, 1, 1, 1]]
[1, 2, 3, 1, 1, 2, 3, 2, 5, 4, 7, 8, 9].sliced(where: >)
// [[1, 2, 3], [1, 1, 2, 3], [2, 5], [4, 7, 8, 9]]