package main
 
import (
	"fmt"
)
 
 
func double(x int) int {
	return x * 2;
}
 
func fmap(f func (int) int, vs []int) []int {
	rs := make([]int, len(vs))
 
	for i, v := range vs {
		rs[i] = f(v)
	}
 
	return rs
}
 
func main() {
	nums := []int{1, 2, 3}
	d := fmap(double, nums)
 
	fmt.Println(d)
}