How to Read Multiple Integers from Standard Input in Golang Without a For Loop?

Reading Integers Separated by Space in Golang

Question:

How to efficiently read multiple integers from standard input (stdin) and store them in an integer slice without using a for loop in Golang? For example, given the following input:

Enter the number of integers
3
Enter the integers
23 45 66

How to convert these values into an integer slice?

Answer:

Although a loop is inherently present, it's possible to achieve this without using explicit for or goto loops. Here's how:

<code class="go">package main

import "fmt"

func main() {
    fmt.Println(`Enter the number of integers`)
    var n int
    if m, err := Scan(&amp;n); m != 1 {
        panic(err)
    }
    fmt.Println(`Enter the integers`)
    all := make([]int, n)
    ReadN(all, 0, n)
    fmt.Println(all)
}

func ReadN(all []int, i, n int) {
    if n == 0 {
        return
    }
    if m, err := Scan(&amp;all[i]); m != 1 {
        panic(err)
    }
    ReadN(all, i+1, n-1)
}

func Scan(a *int) (int, error) {
    return fmt.Scan(a)
}</code>

Example Input/Output:

Enter the number of integers
3
Enter the integers
10 20 30
[10 20 30]

Optimization for Faster Input Scanning:

To enhance input scanning speed, replace the Scan function with the following optimized version:

<code class="go">func Scan(a *int) (int, error) {
    var buf [10]byte
    var ret int
    for scanned, err := fmt.Scanf("%d%s", &ret, &buf); err == nil && scanned != 2; {
        fmt.Scanf("%s", &buf)
    }
    *a = ret
    return 1, err
}</code>

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