Go Unpacking Array As Arguments

Question

So in Python and Ruby there is the splat operator (*) for unpacking an array as arguments. In Javascript there is the .apply() function. Is there a way of unpacking an array/slice as function arguments in Go? Any resources for this would be great as well!

Something along the lines of this:

func my_func(a, b int) (int) {
    return a + b
}

func main() {
    arr := []int{2,4}
    sum := my_func(arr)
}

I do apologize if I'm making an syntactical/assorted mistakes. I'm new to Go.

Answer 1

You can use a vararg syntax similar to C:

package main
import "fmt"

func my_func( args ...int) int {
   sum := 0
   for _,v := range args {
      sum = sum + v
   }

   return sum;
}

func main() {
    arr := []int{2,4}
    sum := my_func(arr...)
    fmt.Println("Sum is ", sum)
}

Now you can sum as many things as you'd like. Notice the important ... after when you call the my_func function.

Running example: http://ideone.com/8htWfx

Answer 2

Either your function is varargs, in which you can use a slice with the ... notation as Hunter McMillen shows, or your function has a fixed number of arguments and you can unpack them when writing your code.

If you really want to do this dynamically on a function of fixed number of arguments, you can use reflection:

package main
import "fmt"
import "reflect"

func my_func(a, b int) (int) {
    return a + b
}

func main() {
    arr := []int{2,4}
    var args []reflect.Value
    for _, x := range arr {
        args = append(args, reflect.ValueOf(x))
    }
    fun := reflect.ValueOf(my_func)
    result := fun.Call(args)
    sum := result[0].Interface().(int)
    fmt.Println("Sum is ", sum)
}

Answer 3

No, there's no direct support for this in the language. Python and Ruby, as well as Javascript you're mentioning; are all dynamic/scripting languages. Go is way more closer to, for example, C than to any dynamic language. The 'apply' functionality is handy for dynamic languages, but of little use for static languages like C or Go,