动态初始化数组大小。

I try to write a small application in go that takes 'x' numbers of integers from standard input, calculates the mean and gives it back. I have only gotten so far:

我试着写一个小的应用程序，它从标准输入中取“x”的整数，计算平均值，然后返回。到目前为止，我只做到了:

func main() {
var elems, mean int
sum := 0

fmt.Print("Number of elements? ")

fmt.Scan(&elems)

var array = new([elems]int)

for i := 0; i < elems; i++ {
    fmt.Printf("%d . Number? ", i+1)
    fmt.Scan(&array[i])
    sum += array[i];
}............

When trying to compile this I get the following error message:

在尝试编译时，我得到以下错误消息:

invalid array bound elems

无效的数组绑定elem

What is wrong here?

什么是错误的吗?

3 个解决方案

#1

you should use a slice:

你应该使用切片:

//var array = new([elems]int) - no, arrays are not dynamic
var slice = make([]int,elems) // or slice := make([]int, elems)

see "go slices usage and internals"

参见“go slice用法和内部细节”

Also you may want to consider using range for your loop:

你也可以考虑使用范围for your loop:

// for i := 0; i < elems; i++ { - correct but less idiomatic
for i, v := range slice {

#2

In my opinion, this results from confusion over the usage of the new and make functions. This is a known issue/feature in the Go language, as evidenced by several discussions about new vs make at golang-nuts.

在我看来，这是由于对新函数的使用和make函数的混淆造成的。在Go语言中，这是一个众所周知的问题/特性，在golang-nuts会议上关于新vs make的讨论就证明了这一点。

The difference between new and make may become clearer by letting Go print out the type of the value created by new and make:

new和make之间的区别可以通过打印new创建的值的类型而变得更加清晰:

package main

import "fmt"

func main() {
    fmt.Printf("%T  %v\n", new([10]int), new([10]int))
    fmt.Printf("%T  %v\n", make([]int, 10), make([]int, 10))
}

The output:

输出:

*[10]int  &[0 0 0 0 0 0 0 0 0 0]
[]int  [0 0 0 0 0 0 0 0 0 0]

As can be seen from the type, to access an array element of new([10]int) we would first need to dereference the pointer.

从类型中可以看出，要访问new([10]int)的数组元素，我们首先需要取消对指针的引用。

Both new and make require a Go type as their 1st argument. However, the expression [elems]int is not a Go type (unless elems is a Go constant, which isn't the case here).

new和make都需要Go类型作为第一个参数。但是，表达式[elems]int不是Go类型(除非elems是Go常量，这里不是这种情况)。

For further reference, see http://golang.org/doc/go_spec.html#Allocation and http://golang.org/doc/go_spec.html#The_zero_value.

要进一步参考，请参见http://golang.org/doc/go_spec.html#分配和http://golang.org/doc/go_spec.html#The_zero_value。

To get a better understanding of whether the result of new is usable, it may be helpful to lookup whether len and cap work with zero (nil) values: http://golang.org/doc/go_spec.html#Length_and_capacity

要更好地了解new的结果是否可用，可以查找len和cap是否使用0 (nil)值:http://golang.org/doc/go_spec.html#Length_and_capacity

#3

See The Go Programming Language Specification

参见Go编程语言规范

http://golang.org/ref/spec#Array_types

http://golang.org/ref/spec Array_types

http://golang.org/ref/spec#Constants

http://golang.org/ref/spec常量

It says:"The length is part of the array's type; it must evaluate to a non- negative constant representable by a value of type int. "

它说:“长度是数组类型的一部分;它的值必须是非负常数，可以用int类型的值表示。”

Constants by no means vary.

常数绝不是变化的。

#1