布尔运算符

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These can be used inside the condition of an if statement.

这些可以使用于 if 语句中的条件判断。


&& (逻辑与)


True only if both operands are true, e.g.

if (digitalRead(2) == HIGH  && digitalRead(3) == HIGH) { // read two switches 
  // ...
} 

is true only if both inputs are high.


|| (逻辑或)


True if either operand is true, e.g.

if (x > 0 || y > 0) {
  // ...
} 

is true if either x or y is greater than 0.


! (取反)


True if the operand is false, e.g.

if (!x) { 
  // ...
} 

is true if x is false (i.e. if x equals 0).


警告:


Make sure you don't mistake the boolean AND operator, && (double ampersand) for the bitwise AND operator & (single ampersand). They are entirely different beasts.


Similarly, do not confuse the boolean || (double pipe) operator with the bitwise OR operator | (single pipe).


The bitwise not ~ (tilde) looks much different than the boolean not ! (exclamation point or "bang" as the programmers say) but you still have to be sure which one you want where.


示例

if (a >= 10 && a <= 20){}   // true if a is between 10 and 20




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