scala2-3-UsingClauses-example.scala

given evenOdd: Ordering[Int] = new Ordering[Int]:
  def compare(i: Int, j: Int): Int = i%2 compare j%2 match
    case 0 => i compare j
    case c => -c

// Equivalent to the following form:
// given evenOdd2: Ordering[Int] with
//   def compare(i: Int, j: Int): Int = i%2 compare j%2 match
//     case 0 => i compare j
//     case c => -c

val seq = SortableSeq(Seq(1,3,5,2,4))
val expected = SortableSeq(Seq(4, 2, 5, 3, 1))
assert(seq.sortBy1a(i => -i) == expected)
assert(seq.sortBy1b(i => -i) == expected)
assert(seq.sortBy2(i => -i)  == expected)

assert(seq.sortBy1a(i => -i)(using evenOdd) == expected)
assert(seq.sortBy1b(i => -i)(using evenOdd) == expected)
assert(seq.sortBy2(i => -i)(using evenOdd)  == expected)