定義自定義一元運算子

可以通過在運算子前新增 unary_ 來定義一元運算子。一元運算子僅限於 unary_+，unary_-，unary_! 和 unary_~：

class Matrix(rows: Int, cols: Int, val data: Seq[Seq[Int]]){
  def +(that: Matrix) = {
    val newData = for (r <- 0 until rows) yield
      for (c <- 0 until cols) yield this.data(r)(c) + that.data(r)(c)

    new Matrix(rows, cols, newData)
  }

  def unary_- = {
    val newData = for (r <- 0 until rows) yield 
      for (c <- 0 until cols) yield this.data(r)(c) * -1
   
    new Matrix(rows, cols, newData) 
  }   
}

一元運算子可以如下使用：

val a = new Matrix(2, 2, Seq(Seq(1,2), Seq(3,4)))
val negA = -a

這應該與 parcimony 一起使用。使用不符合預期的定義過載一元運算子會導致程式碼混淆。