Question

I have the following function

scala> def f1 = (prefix: String) => prefix + ".field"
f1: String => java.lang.String

And I’d like to define another function from f1, that fixed the value of prefix to p1, like this

def f2: () => String = () => f1("p1")

or more shortly

def f2 = () => f1("p1")

I think that the same could be achieved using Function.curried or f.curried and partialy applied functions, but I still couldn’t do it…

—

Having a look a this article I found a more verbose way of defining it. I guess the above syntax is just suger for this longer form…

scala> object f2 extends Function0[String] {
     | override def apply = f1("p1")
     | }
defined module f2

scala> f2
res37: f2.type = <function0>

scala> f2()
res38: java.lang.String = p1.field

Answer 1

You can only “curry” functions with more than one argument. At least with the methods that Scala provides by default. With two parameters it works like this:

val f2 = (prefix: String, foo:String) => prefix + ".field"
val f1 = f2.curried("p1")

If you want to do the same with Function1, you can “pimp” the class to add a new method:

implicit def addCurry[A,B](f:Function[A,B]) = new Function1WithCurried(f)
class Function1WithCurried[-A,+B](f:Function1[A,B]) {
  def curried:Function1[A,Function0[B]] = (x:A) => { () => f(x) }
}

def f1 = (prefix: String) => prefix + ".field"
val f0 = f1.curried
val f2 = f1.curried("p1")