Higher-Order Function are functions that operate onother functions.
Higher-order functions are allowed in Scala, and higher-order functions can use other functions as parameters or functions as output.
In the following example the apply() function takes another function f and the value v as arguments, and function f calls the parameter v:
object Test {
def main(args: Array[String]) {
println( apply( layout, 10) )
}
// Function f and value v are used as parameters, while function f calls parameter v
def apply(f: Int => String, v: Int) = f(v)
def layout[A](x: A) = "[" + x.toString() + "]"
}
Execute the above code, and the output is as follows:
$ scalac Test.scala
$ scala Test
[10]