How Can I Efficiently Read Multiple Numbers into a Go Slice Using fmt.Fscan?

Reading Numbers into Slices Using fmt.Fscan

To read multiple numbers into an array or slice in Go using fmt.Fscan, it is common practice to declare individual variables and provide their addresses as arguments:

numbers := make([]int, 2)
fmt.Fscan(os.Stdin, &numbers[0], &numbers[1])

However, it is not possible to directly pass the slice itself as a parameter to fmt.Fscan. To simplify this process, you can create a utility function that packs the addresses of the slice elements:

func packAddrs(n []int) []interface{} {
    p := make([]interface{}, len(n))
    for i := range n {
        p[i] = &n[i]
    }
    return p
}

Using this function, you can now scan a whole slice with fmt.Fscan:

numbers := make([]int, 2)
n, err := fmt.Fscan(os.Stdin, packAddrs(numbers)...) // ... unpacks the slice addresses
fmt.Println(numbers, n, err)

For example, consider the following test input:

1 3 5 7 9

Using fmt.Sscan for testing purposes:

numbers := make([]int, 5)
n, err := fmt.Sscan("1 3 5 7 9", packAddrs(numbers)...)
fmt.Println(numbers, n, err) // Output: [1 3 5 7 9] 5 <nil></nil>

This demonstrates how to efficiently read multiple numbers into a slice using fmt.Fscan.

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