将按名称参数传播到函数调用

Question

Inside the body of a function that has a "By-name" parameter "f", I want to call another function and pass that parameter inside it. Specifically, I want to pass a "block" of code inside my timeit function:

def warmUpAndMeasure(f: =>Int) = {
  val minimumTimeTaken = common.utils.timeit(
    repeat = 20, 
    assertResult = Some(148848)) {
      f
    }
  println(s"Best execution took $minimumTimeTaken ms.")
}
warmUpAndMeasure { antFunctional.funcs.walk(1000,1000) }

Starting from the last line of the code, I call warmUpAndMeasure passing inside it a code block. warmUpAndMeasure is in turn supposed to pass that block into common.utils.timeit , but setting it up first so that it will repeatedly (20 times) call the passed in code block, verifying that each time it returns 148848, and reporting at the end, the minimum time taken to execute the block (out of all 20 times).

I am new to Scala, and so far, the only way I've found out to pass f as-is into timeit (and not call it!) - as you can see in the code above - is to write another nameless code block: { f } . Is there any other way to specify that I want f to pass in, not be called at the invocation of timeit ?

EDIT : Clarifying - my code above works, but I am just asking whether there's a better way to "delay the evaluation" of parameter f other than writing another block (as I did). Here's the code for my timeit , for reference:

def timeit[A](repeat:Int=20, assertResult:Option[A] = None)(f: => A) = {
  val minimumTime = List.range(1,repeat+1).map {
    idx => {
      if (idx == 1)
        print("Benchmark iteration:     ")
      print("\b\b\b\b%4d" format idx)
      val startTime = System.currentTimeMillis
      val result = f
      var totalTime = System.currentTimeMillis - startTime
      assertResult match {
        case Some(value) => {
          try { assert(value == result) }
          catch { case e:AssertionError =>
            println("\nExpected:" + value + ", got:" + result) ; throw e
          }
        }
        case None => ()
      }
      totalTime
    }
  }.min
  print("\n")
  minimumTime
}

Answer 1

显然，我唯一缺少的是我可以在括号内传递f （谢谢@vptheron）。

common.utils.timeit(repeat = 20, assertResult = Some(148848))(f)