Defining a function with multiple implicit arguments in Scala

Question

How can I define a function with multiple implicit arguments.

def myfun(arg:String)(implicit p1: String)(implicit p2:Int)={} // doesn\'t work

Answer 1

There actually is a way of doing exactly what the OP requires. A little convoluted, but it works.

class MyFunPart2(arg: String, /*Not implicit!*/ p1: String) {
  def apply(implicit p2: Int) = {
    println(arg+p1+p2)
    /* otherwise your actual code */
  }
}

def myFun(arg: String)(implicit p1: String): MyFunPart2= {
  new MyFunPart2(arg, p1)
}

implicit val iString= " world! "
implicit val iInt= 2019

myFun("Hello").apply
myFun("Hello")(" my friend! ").apply
myFun("Hello")(" my friend! ")(2020)

//  Output is:
//      Hello world! 2019
//      Hello my friend! 2019
//      Hello my friend! 2020

In Scala 3 (a.k.a. "Dotty", though this is the compiler's name) instead of returning an auxiliary MyFunPart2 object, it's possible to return a function value with implicit arguments directly. This is because Scala 3 supports "Implicit Functions" (i.e. "parameter implicitness" now is part of function types). Multiple implicit parameter lists become so easy to implement that it's possible the language will support them directly, though I'm not sure.