implicit

test.sc

trait CanTruthy[A] {
    def truthys(a: A): Boolean
}

object CanTruthy {
    def apply[A](implicit ev: CanTruthy[A]): CanTruthy[A] = ev
    def truthys[A](f: A => Boolean): CanTruthy[A] = new CanTruthy[A] {
        def truthys(a: A): Boolean = f(a)
    }
}

trait CanTruthyOps[A] {
    def self: A
    implicit def F: CanTruthy[A]
    final def truthy: Boolean = F.truthys(self)
}

object ToCanIsTruthOps {
    implicit def toCanIsTruthyOps[A](v: A)(implicit ev: CanTruthy[A]) =
        new CanTruthyOps[A] {
            def self = v
            override implicit def F: CanTruthy[A] = ev
        }
}

import ToCanIsTruthOps._

implicit val intCanTruthy: CanTruthy[Int] = CanTruthy.truthys({
    case 0 => false
    case _ => true
})

def truthyIf[A: CanTruthy, B, C](cond: A)(ifyes: => B)(ifno: => C) =
    if (cond.truthy) ifyes
    else ifno

println(truthyIf(12){"YES"}{"NO"})