Question

与之相关的区别 Operator Priority使用前缀和后缀

    // program 01

    int x =10;
    int c = x++ + ++x;
    Console.WriteLine(c); // output will be 22

    // program 02

    int x =10;
    int c = ++x + x++;
    Console.WriteLine(c); // output will be 22

    // program 03

    int x =10;
    int c = ++x + x;
    Console.WriteLine(c); // output will be 22

Answer 1

以下是评估这些表达式的方法：

1：

x++ + ++x;
 |  |  |
 1  3  2

1: increments x to 11, returns value before increment (10)
2: increments x to 12, returns value after increment (12)
3: 10 + 12 = 22

2：

++x + x++;
 |  |  |
 1  3  2

1: increments x to 11, returns value after increment (11)
2: increments x to 12, returns value before increment (11)
3: 11 + 11 = 22

3：

++x + x
 |  | |
 1  3 2

1: increments x to 11, returns value after increment (11)
2: returns value of x (11)
3: 11 + 11 = 22

值得注意的是，某些C / C ++实现可能会以不同的顺序评估此表达式。此页面包含与OP相同的未定义行为的示例。 http://en.cppreference.com/w/cpp/language/eval_order

c＃ - 与运算符优先级混淆

1 个答案: