c++ - 为什么尽管我的函数和 cout 语句放置错误，我的程序仍能运行？

Question

理想情况下，我的华氏函数的一些内容应该放在主函数中，但想尝试一下。我要求用户在华氏函数中输入，之后，我在cout之后调用了华氏函数。陈述。我期望首先显示“您的温度...”字符串，但它在继续打印字符串之前要求输入。为什么会这样？

#include <iostream>
using namespace std;
int FahrenheitConv();
int main ()
{
    cout << "Your temperature in Fahrenheit is "<< FahrenheitConv();
    return 0;
}

int FahrenheitConv()
{
    double centigrade;
    cout << "What is your temperature in centigrade: ";
    cin >> centigrade;

    double fahrenheit = (1.8) * (centigrade ) + 32;
    return fahrenheit;
}

Answer 1

根据N4296 :

1.9 Program Execution [intro.execution]

[...] Except where noted, evaluations of operands of individual operators and of subexpressions of individual expressions are unsequenced. [ Note: In an expression that is evaluated more than once during the execution of a program, unsequenced and indeterminately sequenced evaluations of its subexpressions need not be performed consistently in different evaluations. — end note ] [...]

因此，您不能真正期望任何特定的顺序，除非对于真正特定的情况，例如逻辑运算符和三元运算符，它们引入了序列点。