Suppose I would like to apply a function to every element in a list, and then put the resulting values in another list so I can immediately use them. In python, I would do something like this:
list = [1,2,3]
str = ', '.join(multiply(x, 2) for x in list)
In Go, I do something like this:
list := []int{1,2,3}
list2 := []int
for _,x := range list {
list2 := append(list2, multiply(x, 2))
}
str := strings.Join(list2, ", ")
Is it possible to do this in a shorter way?
I would do exactly as you did, with a few tweaks to fix typos
import (
"fmt"
"strconv"
"strings"
)
func main() {
list := []int{1,2,3}
var list2 []string
for _, x := range list {
list2 = append(list2, strconv.Itoa(x * 2)) // note the = instead of :=
}
str := strings.Join(list2, ", ")
fmt.Println(str)
}
This is an old question, but was the top hit in my Google search, and I found information that I believe will be helpful to the OP and anyone else who arrives here, looking for the same thing.
There is a shorter way, although you have to write the map function yourself.
In go, func
is a type, which allows you to write a function that accepts as input the subject slice and a function, and which iterates over that slice, applying that function.
See the Map
function near the bottom of this Go by Example page : https://gobyexample.com/collection-functions
I've included it here for reference:
func Map(vs []string, f func(string) string) []string {
vsm := make([]string, len(vs))
for i, v := range vs {
vsm[i] = f(v)
}
return vsm
}
You then call it like so:
fmt.Println(Map(strs, strings.ToUpper))
So, yes: The shorter way you are looking for exists, although it is not built into the language itself.
Found a way to define a generic map array function
func Map(t interface{}, f func(interface{}) interface{} ) []interface{} {
switch reflect.TypeOf(t).Kind() {
case reflect.Slice:
s := reflect.ValueOf(t)
arr := make([]interface{}, s.Len())
for i := 0; i < s.Len(); i++ {
arr[i] = f(s.Index(i).Interface())
}
return arr
}
return nil
}
origin := []int{4,5,3}
newArray := Map(origin, func(item interface{}) interface{} { return item.(int) + 1})