I'm trying to use the Scala extensions to extend the String context to time the execution of a costly method And I came with this:

extension(sc: StringContext)
  def timeit(args: Any*): String = {
    val startTime = System.currentTimeMillis();
    // sc.parts.evaluate??
    val result = sc.s(args*) + s.parts().mkstring("");
    result + " took " + (System.currentTimeMillis() - startTime) + " millisecs"
  }

Unfortunately I don't see a way to intercept before the sc.parts are evaluated, so there is not much sense in measuring time. Is there a way to record the startTime before the sc.parts are evaluated? Do a call by name somehow? Or some other ways?

I'm trying to use the Scala extensions to extend the String context to time the execution of a costly method And I came with this:

extension(sc: StringContext)
  def timeit(args: Any*): String = {
    val startTime = System.currentTimeMillis();
    // sc.parts.evaluate??
    val result = sc.s(args*) + s.parts().mkstring("");
    result + " took " + (System.currentTimeMillis() - startTime) + " millisecs"
  }

Unfortunately I don't see a way to intercept before the sc.parts are evaluated, so there is not much sense in measuring time. Is there a way to record the startTime before the sc.parts are evaluated? Do a call by name somehow? Or some other ways?

• scala
• string-interpolation
• scala-extension

Share Improve this question Follow asked Mar 23 at 20:54 dr jerrydr jerry 10k2525 gold badges8585 silver badges127127 bronze badges 1

• IIRC, you need to use inline and a macro in order to receive the parts as the original expressions rather than as the results. – Luis Miguel Mejía Suárez Commented Mar 23 at 21:21

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1 Answer 1

Sorted by: Reset to default 3

You need to use inline def, but you also need to make sure that all arguments are inline as well (so that their code would be inlined, not their result):

// code where all arguments are inlined
extension(inline sc: StringContext)
  inline def timeit(inline args: Any*): String = {
    val startTime = System.currentTimeMillis()
    val result = sc.s(args*)
    val endTime = System.currentTimeMillis()
    s"$result took ${endTime - startTime} millisecs"
  }

println(timeit"This string ${ { Thread.sleep(100); "is" } } taking ${ { Thread.sleep(250); "a while" } }")

// code where arguments are NOT inlined
extension(sc: StringContext)
  inline def timeit2(args: Any*): String = {
    val startTime = System.currentTimeMillis()
    val result = sc.s(args*)
    val endTime = System.currentTimeMillis()
    s"$result took ${endTime - startTime} millisecs"
  }

println(timeit2"This string ${ { Thread.sleep(100); "is" } } taking ${ { Thread.sleep(250); "a while" } }")

This string is taking a while took 354 millisecs
This string is taking a while took 1 millisecs