duanning9110
duanning9110
2015-11-10 14:30
浏览 36
已采纳

如何在Go中分配一个浮点数?

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

Question:

  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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2条回答 默认 最新

  • douqie6454
    douqie6454 2015-11-10 14:34
    已采纳

    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
    

    with

    xs := make([]float64, 10)
    

    which will give it the right size initially.

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  • dtzk85937
    dtzk85937 2015-11-10 15:30

    @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 (
        "fmt"
        "math/rand"
        "time"
    )
    
    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()
        }
    
        fmt.Println(xn)
    }
    
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