Scala Note 20: Higher-Order & Anonymous Functions

Higher-Order functions are functions that take other functions as parameters, or whose result is a function.

class Decorator(left: String, right: String) {
  def layout[A](x: A) = left + x.toString() + right
}

object FunTest extends Application {
  def apply(f: Int => String, v: Int) = f(v)
  val decorator = new Decorator("[", "]")
  println(apply(decorator.layout, 7))
}

The type Int => String is the type of functions that take arguments of type Int and return results of type String.
Here is a function apply which takes another function f and a value v and applies function f to v:

Anonymous Functions:

An anonymous function is an expression that evaluates to a function; the function is defined without

giving it a name.

(x: Int) => x * x

The part before the arrow ‘=>’ are the parameters of the function, whereas the part
following the ‘=>’ is its body. The Scala compiler can deduce the parameter type(s) fromthe context of the anonymous function in which case they can be omitted.

Reference:
http://www.scala-lang.org/old/node/134.html