Kotlin: Idiomatic Call Method (Int, Int) & # 8594; Int with a pair <Int, Int>?

Question

fun sum(a: Int, b: Int) = a + b
val x = 1.to(2)

I'm looking for:

• sum.tupled(x), or
• sum(*x)

Of course, none of the above compilations with Kotlin 1.1.3-2. So what am I stuck with sum(x.first, x.second)?

Edit

Summarizing the useful answers, I think this is now the closest:

fun <P1, P2, R> Function2<P1,P2,R>.tupled(x: Pair<P1, P2>): R = invoke(x.first, x.second)

Answer 1

After you find out about your needs, I think you don’t need overload / extension functions at all, just using KCallable # call , for example:

val x  = arrayOf(1, 2)

//                v--- top-level  functions 
val result:Int = ::sum.call(*x) 
//                  v--- member-level  functions 
val result:Int = this::sum.call(*x) 

---

You can also overload a function sumin Kotlin in the same way as Java, for example:

sum(1 to 2)
sum(*intArrayOf(1, 2))

fun sum(tuple: Pair<Int, Int>) = sum(tuple.first, tuple.second)

fun sum(vararg pair: Int) = sum(pair[0], pair[1])

---

For sum.tupled(x)you can write an extension function, for example:

val sum: (Int, Int) -> Int = ::sum // top-level function
//OR
val sum:(Int, Int)->Int = this::sum // member scope function


// the final form is what you want 
//                       v
val result:Int = sum.tupled(1 to 2)

fun <T1,T2,R> Function2<T1,T2,R>.tupled(x:Pair<T1,T2>):R = invoke(x.first,x.second)

Answer 2

Sotary Kotlin, :

val sum : (Pair<Int,Int>) -> Int = { (a,b) -> a + b }

Answer 3

:

fun Pair<Int, Int>.sum() = this.first + this.second
val x = 1.to(2)
x.sum()