Question

根据此处的优先顺序，有些人可以解释以下内容如何工作：http://en.cppreference.com/w/cpp/language/operator_precedence

假设：

#include <cstdio>

#define MY_CONSTANT 5.6

int main(int argc, char ** argv) {
    const double calculatedValue = 4.4;
    const double myValue = MY_CONSTANT + 1 ? 4.4 : -4.4;

    printf("%f\n", myValue);
    return 1;
}

我希望

myValue == 10

我得到了

myValue == 4.4;

Answer 1

const double myValue = (MY_CONSTANT + 1) ? 4.4 : -4.4;

相当于：

?:

因为+的前导值低于C ++运算符优先级表中的(MY_CONSTANT + 1)

由于4.4评估为非零，因此myvalue为10。

要将const double myValue = MY_CONSTANT + (1 ? 4.4 : -4.4); // ^ ^作为输出，您需要显式括号来更改评估顺序：

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三元算子和加法优先

1 个答案: