英文:
How can I define a `const *DataType`
问题
我正在使用Go语言编写一个Lisp变种，并且想要为Nil和EmptyList定义常量。这些常量将在整个代码库中被引用，但我希望防止它们被意外重新定义。
// 空列表的表示
var EmptyList = (*List)(nil)
在这里我不能使用const的原因有两个：
const定义不能是nilconst定义不能是指针
我有哪些选项可以确保EmptyList始终是nil指针？
英文:
I'm writing a Lisp variant in Go and want to define constants for Nil and EmptyList. These will be referenced throughout the codebase, but I want to prevent them from being accidentally re-defined.
// Representation of the empty list
var EmptyList = (*List)(nil)
I can't use a const here for two reasons:
constdefinitions cannot benilconstdefinitions cannot be pointers
What options do I have to ensure EmptyList is always the nil pointer?
答案1
得分: 1
在Go语言中，可以使用函数。例如，
package main
import "fmt"
type List struct{}
func IsEmptyList(list *List) bool {
// 表示空列表
return list == (*List)(nil)
}
func main() {
fmt.Println(IsEmptyList((*List)(nil)))
}
输出结果：
true
该函数将被内联。
$ go tool compile -m emptylist.go
emptylist.go:7: can inline IsEmptyList
emptylist.go:13: inlining call to IsEmptyList
emptylist.go:7: IsEmptyList list does not escape
emptylist.go:13: IsEmptyList((*List)(nil)) escapes to heap
emptylist.go:13: main ... argument does not escape
$
英文:
In Go, use a function. For example,
package main
import "fmt"
type List struct{}
func IsEmptyList(list *List) bool {
// Representation of the empty list
return list == (*List)(nil)
}
func main() {
fmt.Println(IsEmptyList((*List)(nil)))
}
Output:
true
The function will be inlined.
$ go tool compile -m emptylist.go
emptylist.go:7: can inline IsEmptyList
emptylist.go:13: inlining call to IsEmptyList
emptylist.go:7: IsEmptyList list does not escape
emptylist.go:13: IsEmptyList((*List)(nil)) escapes to heap
emptylist.go:13: main ... argument does not escape
$
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