英文:
Go tour #18. How do I pass in integers to Pic?
问题
以下是代码的中文翻译：
package main
import "golang.org/x/tour/pic"
func Pic(dx, dy int) [][]uint8 {
mypic := [][]uint8{}
for y := 0; y < dy; y++ {
mypic = append(mypic, []uint8{})
for x := 0; x < dx; x++ {
mypic[y] = append(mypic[y], uint8((x + y) / 2))
}
}
return mypic
}
func main() {
pic.Show(Pic)
}
这段代码出现了索引超出范围的错误。我尝试将main函数修改为pic.Show(Pic(500, 500))，但这样会将参数从函数改为返回类型，导致编译失败。如果pic.Show期望一个函数作为参数，我该如何传入整数呢？
英文:
The following code errors with index out of range. I tried modifying main to
pic.Show(Pic(500, 500)) but that changes the argument from function to the return type and it fails to compile. How do I pass in integers if the pic.Show is expecting a function as an argument.
package main
import "golang.org/x/tour/pic"
func Pic(dx, dy int) [][]uint8 {
mypic := [][]uint8{}
for y := 0; y < dy; y++ {
mypic[y] = []uint8{}
for x := 0; x < dx; x++ {
mypic[y][x] = uint8((x + y) / 2)
}
}
return mypic
}
func main() {
pic.Show(Pic)
}
答案1
得分: 2
你不需要这样做。Go Tour程序将会向你的程序传递Pic测试值。你的问题出在你的代码上：panic: runtime error: index out of range。[][]uint8{}和[]uint8{}分别分配了零个y和零个x切片元素。使用make来分配你的y和x切片。例如，
package main
import "golang.org/x/tour/pic"
func Pic(dx, dy int) [][]uint8 {
pixels := make([][]uint8, dy)
for y := 0; y < dy; y++ {
pixels[y] = make([]uint8, dx)
for x := 0; x < dx; x++ {
pixels[y][x] = uint8((x + y) / 2)
}
}
return pixels
}
func main() {
pic.Show(Pic)
}
参考：Making slices, maps and channels, The Go Programming Language Specification
英文:
You don't. The Go Tour program will pass Pic test values to your program. Your problem is in your code: panic: runtime error: index out of range. [][]uint8{} and []uint8{} allocate zero y and zero x slice elements. Use make to allocate your y and x slices. For example,
package main
import "golang.org/x/tour/pic"
func Pic(dx, dy int) [][]uint8 {
pixels := make([][]uint8, dy)
for y := 0; y < dy; y++ {
pixels[y] = make([]uint8, dx)
for x := 0; x < dx; x++ {
pixels[y][x] = uint8((x + y) / 2)
}
}
return pixels
}
func main() {
pic.Show(Pic)
}
Reference: Making slices, maps and channels, The Go Programming Language Specification
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