Issue
In Golang, how can I iterate over three slices with a single for loop, without creating a new slice containing copies of the elements in all three slices? Is there something like Python’s itertools.chain?
Solution
A simple solution using generics
package main
import "fmt"
func Chain[T any](f func(e T), slices ...[]T) {
for _, slice := range slices {
for _, e := range slice {
f(e)
}
}
}
func main() {
slice1 := []int{1, 2, 3}
slice2 := []int{10, 20, 30}
slice3 := []int{100, 200, 300}
Chain(func(e int) {
fmt.Println(e)
}, slice1, slice2, slice3)
}
Output:
1
2
3
10
20
30
100
200
300
The function Chain takes a function parameter, which will be executed for each element in each slice consecutively. This function will serve as your loop body code.
The solution can be extended to retain other looping features such as break and index numbers:
func Chain[T any](f func(i int, e T) bool, slices ...[]T) {
var i int
for _, slice := range slices {
for _, e := range slice {
if !f(i, e) {
return
}
i++
}
}
}
...
Chain(func(i int, e int) bool {
fmt.Println(i, "-", e)
return (e <= 20)
}, slice1, slice2, slice3)
...
The loop will "break" when f returns false.
Output:
0 - 1
1 - 2
2 - 3
3 - 10
4 - 20
5 - 30
Answered By – Hymns For Disco
Answer Checked By – Mary Flores (GoLangFix Volunteer)