Short way to apply a function to all elements in a list in golang

Question

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?

Answer 1

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)
}

Answer 2

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.