逻辑和运算符短路

&&优先于||，这意味着放置括号来评估将一起评估的内容。

c ++在&&和||中使用短路评估不做不必要的处决。
如果是||的左侧返回 true，右侧不再需要评估。

#include <iostream>
#include <string>

using namespace std;

bool True(string id){
    cout << "True" << id << endl;
    return true;
}

bool False(string id){
    cout << "False" << id << endl;
    return false;
}

int main(){
    bool result;
    //let's evaluate 3 booleans with || and && to illustrate operator precedence
    //precedence does not mean that && will be evaluated first but rather where    
    //parentheses would be added
    //example 1
    result =
        False("A") || False("B") && False("C"); 
                // eq. False("A") || (False("B") && False("C"))
    //FalseA
    //FalseB
    //"Short-circuit evaluation skip of C"
    //A is false so we have to evaluate the right of ||,
    //B being false we do not have to evaluate C to know that the result is false
    

    
    result =
        True("A") || False("B") && False("C"); 
                // eq. True("A") || (False("B") && False("C"))
    cout << result << " :=====================" << endl;
    //TrueA
    //"Short-circuit evaluation skip of B"
    //"Short-circuit evaluation skip of C"
    //A is true so we do not have to evaluate 
    //        the right of || to know that the result is true
    //If || had precedence over && the equivalent evaluation would be:
    // (True("A") || False("B")) && False("C")
    //What would print
    //TrueA
    //"Short-circuit evaluation skip of B"
    //FalseC
    //Because the parentheses are placed differently 
    //the parts that get evaluated are differently
    //which makes that the end result in this case would be False because C is false
}