test.scala

def foo(implicit n: 42) = { n + 1 }

implicit n = 55;

foo // 56

trait ConcurrentRunner { def run() }

class NilRunner < ConncurrentRunner;
class ThreadPoolRunner < ConncurrentRunner;
class RealConcurrentRunner < ConncurrentRunner;


def foo(implicit runner) { runner.run { future { // heavry job... }}
 

implicit runner = NIlRUnner

Future { 42 }.map { _ + 1 }.filter { _ > 0 }