“数组边界不是整数常量”在类中定义数组大小时，使用 const 数组的元素
#ifndef QWERT_H
#define QWERT_H
const int x [] = {1, 2,};
const int z = 3;
#endif
#include <iostream>
#include "qwert.h"
class Class
{
int y [x[0]]; //error:array bound is not an integer constant
int g [z]; //no problem
};
int main ()
{
int y [x[0]]; //no problem
Class a_class;
}
我不明白为什么这不起作用。其他遇到此问题的人似乎正在尝试动态分配数组。非常感谢任何帮助。
#ifndef QWERT_H
#define QWERT_H
const int x [] = {1, 2,};
const int z = 3;
#endif
#include <iostream>
#include "qwert.h"
class Class
{
int y [x[0]]; //error:array bound is not an integer constant
int g [z]; //no problem
};
int main ()
{
int y [x[0]]; //no problem
Class a_class;
}
I can't figure out why this doesn't work. Other people with this problem seem to be trying to dynamically allocate arrays. Any help is much appreciated.
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评论（3）
x 是 const（显然 z 也是），但 x[0] 不是常量表达式。类定义中的数组声明必须具有常量大小说明符。
考虑一下这个问题；如果类在编译时包含未知大小的数组，您如何期望 sizeof 运算符来评估类的大小？
x is const (as is z obviously), but x[0] is not a constant expression. Array declarations in a class definition must have constant size specifiers.
Consider this for a moment; how would you expect the sizeof operator to evaluate the size of your class if it contains an array of unknown size at compile time?
主要版本之所以有效，是因为您的编译器具有允许可变长度数组的扩展。在C++03中数组访问不能是常量表达式，即使数组和索引都是常量表达式，这就是错误的根源。
The main version works because your compiler has an extension to allow for variable length arrays. Array accesses cannot be constant expressions in C++03, even if the array and the index are both constant expressions, which is the source of the error.
数组的大小必须是常量表达式。我不认为数组中的常量元素符合这样的条件。
main() 中工作的版本可能是由于编译器扩展所致。
The size of an array must be a constant expression. I don't believe that constant elements in an array qualify as such.
The version in main() working is probably due to a compiler extension.