Golang 索引超出范围

Question

我想举一个 Golang 的简单例子。该示例位于 golang 之旅的第 36º 页中。这是我的代码:

package main

import "code.google.com/p/go-tour/pic"
import "fmt"

func Pic(dx, dy int) [][]uint8 {
    dx8 := uint8(dx)

    s1 := make ([][] uint8, dy)
    fmt.Printf("%d\n", len(s1), cap(s1))

    for i := range s1{
        fmt.Printf("%d\n",i)
        for j := range s1 {
            fmt.Printf("%d\n",j)
            s1[i][j] = dx8    
        }
    }

    return s1
}

func main() {
    pic.Show(Pic)
}

我得到的错误:

    256
%!(EXTRA int=256)0
0
panic: runtime error: index out of range

goroutine 1 [running]:
panic(0x18b820, 0x1040a010)
    /usr/local/go/src/runtime/panic.go:464 +0x700
main.Pic(0x100, 0x100, 0x0, 0x0, 0x0, 0x0)
    /tmp/sandbox716191956/main.go:17 +0x4e0
code.google.com/p/go-tour/pic.Show(0x1d7988, 0x104000e0)
    /go/src/code.google.com/p/go-tour/pic/pic.go:20 +0x60
main.main()
    /tmp/sandbox716191956/main.go:26 +0x20

Program exited.

我只想返回 Show 函数使用的双向 slice 。

Answer 1

您需要为图片的两个维度(dy 和 dx)制作 slice 。例如，

package main

import "golang.org/x/tour/pic"

func Pic(dx, dy int) [][]uint8 {
    p := make([][]uint8, dy)
    for i := range p {
        p[i] = make([]uint8, dx)
        for j := range p[i] {
            p[i][j] = uint8(i * j)
        }
    }
    return p
}

func main() {
    pic.Show(Pic)
}