2015-11-10 14:30



I'm learning Go programming and try to test the following average function:

func average(xs []float64) float64 {
    total := 0.0
    for _, v := range xs {
        total += v
    return total / float64(len(xs))

I tried to generate a slice of random float numbers by:

var xs []float64
for n := 0; n < 10; n++ {
    xs[n] = rand.Float64()

however, I got

panic: runtime error: index out of range


  1. How to generate a slice of random number in Golang?
  2. Is expression or function call, like xs := []float64 { for ... } allowed in slice literals?
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  • douqie6454 douqie6454 6年前

    Your method of generating the random numbers is fine, however xs is empty, and Go doesn't automatically extend slices. You could use append, however since you know the size in advance, it's most efficient to replace

    var xs []float64


    xs := make([]float64, 10)

    which will give it the right size initially.

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  • dtzk85937 dtzk85937 6年前

    @hobbs answered the part about your error, but still your solution will give you the same array every time you run it because you are not passing a random seed. I would do something like this:

    package main 
    import (
    func main() {
        s := rand.NewSource(time.Now().UnixNano())
        r := rand.New(s)
        xn := make([]float64, 10)
        for n := 0; n < 10; n++ {
            xn[n] = r.Float64()
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