Scala snippet of the day
The following is useful for benchmarking code from inside the REPL:
def timed(op: => Unit) = {
val start = System.nanoTime
op
(System.nanoTime - start) / 1e9
}
Then you can use it like this:
scala> timed { Thread.sleep(5000) }
res0: Double = 5.010083526
That's syntactic sugar for an anonymous function definition and a call of timed. If a function takes only a single parameter you can pass it inside { }, so if we wrote that out longhand it would be:
scala> def fn = Thread.sleep(5000) fn: Unit scala> timed(fn) res0: Double = 5.010088248
The other neat bit is the use of Scala's pass-by-name mechanism to pass the op parameter. That's the funny-looking op: => Unit argument list to timed. Normally Scala uses by-value parameters, i.e. the line timed(fn) would result in the evaluation of fn, and then passing the returned value (in this case, nothing) into timed. However by using pass-by-name, the evaluation of fn takes place inside timed, and by wrapping it inside timing instrumentation we can time how long op takes to execute.
