Declare slice or make slice?

Question

In Go, what is the difference between var s []int and s := make([]int, 0)?

I find that both works, but which one is better?

Answer 1

In addition to fabriziom's answer, you can see more examples at "Go Slices: usage and internals", where a use for []int is mentioned:

Since the zero value of a slice (nil) acts like a zero-length slice, you can declare a slice variable and then append to it in a loop:

// Filter returns a new slice holding only
// the elements of s that satisfy f()
func Filter(s []int, fn func(int) bool) []int {
    var p []int // == nil
    for _, v := range s {
        if fn(v) {
            p = append(p, v)
        }
    }
    return p
}

It means that, to append to a slice, you don't have to allocate memory first: the nil slice p int[] is enough as a slice to add to.