log-formatter-type-class.scala

abstract class LogFormatter[-A] {
  def format(a: A): String
}

object LogFormatter {
  implicit object StringLogFormatter extends LogFormatter[String] {
    def format(s: String) = s
  }

  implicit object ExceptionLogFormatter extends LogFormatter[Exception] {
    def format(e: Exception) = e.getMessage
  }
}

object Logger {
  def log(level: Int) = new {
    def apply[A: LogFormatter](a: A) {
      val formatted = implicitly[LogFormatter[A]].format(a)
    }
  }
}

val x = Logger.log(0)
x("s")
x(new RuntimeException("bang!"))