ES.41: If in doubt about operator precedence, parenthesize
ES.41: 如果对操作符的优先级有疑问，使用括号明确运算次序
Reason（原因）
Avoid errors. Readability. Not everyone has the operator table memorized.
避免错误。可读性。不是所有人都记住操作符表。
Example（示例）
const unsigned int flag = 2;
unsigned int a = flag;
if (a & flag != 0) // bad: means a&(flag != 0)
Note: We recommend that programmers know their precedence table for the arithmetic operations, the logical operations, but consider mixing bitwise logical operations with other operators in need of parentheses.
注意：我们建议程序员记住数学运算，逻辑运算的优先级（而不适用括号，译者注）。但认为位操作和其他操作符混用时应该使用括号。
if ((a & flag) != 0) // OK: works as intended
Note（注意）
You should know enough not to need parentheses for:
你应该可以理解下面的代码不需要括号。
if (a < 0 || a <= max) {
// ...
}
Enforcement（实施建议）
-
Flag combinations of bitwise-logical operators and other operators.
-
标记将位操作和其他操作混用的情况。
-
Flag assignment operators not as the leftmost operator.
-
标记赋值运算符不在最左侧的情况。
-
???
原文链接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#es40-avoid-complicated-expressions
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