c++ - 按位运算结果和 bool 值

Question

令我沮丧的代码如下:

bool a = 0x00000FF0 & 0x00000FF0 == 0x00000FF0;
if (a) {
  Serial.println("True");
} else {
  Serial.println("False");
}

这会打印“False”。我真的不明白为什么。 更多测试:

bool a = 0x00000FF0 & 0x00000FF0 == 0x00000FF0;
Serial.println(a);

打印0。

和:

unsigned long a = 0x00000FF0 & 0x00000FF0;
Serial.println(a, HEX);

打印FF0。

Answer 1

运算符优先级，编译有警告:

warning: suggest parentheses around comparison in operand of ‘&’ [-Wparentheses]

更改为

bool a = (0x00000FF0 & 0x00000FF0) == 0x00000FF0;