ES.21: 不要在不需要时引入变量(或常量)
Readability. To limit the scope in which the variable can be used.
可读性。为了限定变量可用的作用域。
Example(示例)
int x = 7;
// ... no use of x here ...
++x;
Flag declarations that are distant from their first use.
标记远离首次使用代码的变量定义。
原文链接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#es21-dont-introduce-a-variable-or-constant-before-you-need-to-use-it