Equality of functions in Scala, is functions objects in Scala?

Question

I am reading the book Programming in Scala. In the book, it says that \"A function literal is compiled into a class that when instantiated at runtime is a function value\".

Answer 1

Lambda are compiled as anonymous classes (not case class, as far as I remember). That means if you do:

val f1: (String) => String = _ => "F1"
val f2: (String) => String = _ => "F2"

Both f1 and f2 are subtype of Function1[String,String], but they are of different anonymous classes, so can't equal.

If you write it as:

case class F(res: String) extends ((String) => String) {
  def apply(s: String) = res
}

Then:

val f1: (String) => String = F("A")
val f2: (String) => String = F("A")
f1 == f2 // true