NOTE: Current response by @dsyme is here: #243 (comment) Submitted by exercitus vir on 4/12/2014 12:00:00 AM 392 votes on UserVoice prior to migration (Updated the suggestion to "type clas...

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val f: Int => String = {
 case 0 => "Zero"
}

println(f.isInstanceOf[PartialFunction[Int, String]])
println(f.getClass.getName)

trait Mapper[K, V] {
 def map(k: K): V
}

class MyStream[T] (val value: T) {
 def print = { println(s"value is ${value}") }
 
 def map[T2](mapper: Mapper[T, T2]): MyStream[T2]  = {
   println(s"Mapper overload")
   new MyStream(mapper.map(value))
 }
 
 def map[T2](func: (T) => T2): MyStream[T2] = {
   println(s"Func overload")
   new MyStream(func(value))
 }
}

val s = new MyStream[(String, String)](("key", "value"))

def run[T](msg: String)(expr: => T): T = {
 println(s"\n\n** ${msg} **")
 expr
}


run("proper Mapper passed") {
 s.map(new Mapper[(String, String), String]{
   override def map(keyVal: (String, String)) = keyVal._1
 }).print
}


run("lambda 1") {
 s.map((keyVal: (String, String)) => keyVal._1).print
}

run("lambda 2") {
 s.map(_._1).print
}


// for some reason, this doesn't work with Flink's DataStream[(String, String)]
run("lambda with case") {
 s.map { case (key, value) => key }.print
}